UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. __)* Tenaris S.A. -------------------------------------------------------------------------------- (Name of Issuer) Ordinary Shares -------------------------------------------------------------------------------- (Title of Class of Securities) 88031 M 10 9 ------------------------------------------------- (CUSIP Number) December 31, 2002 -------------------------------------------------------------------------------- (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which this Schedule is filed: [ ] Rule 13d-1(b) [ ] Rule 13d-1(c) [X] Rule 13d-1(d) *The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page. The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes). ------------------------ CUSIP NO. 88031 M 10 9 ------------------------ -------------------------------------------------------------------------------- 1. NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) ROBERTO ROCCA -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [ ] (b) [ ] -------------------------------------------------------------------------------- 3. SEC USE ONLY -------------------------------------------------------------------------------- 4. CITIZENSHIP OR PLACE OF ORGANIZATION ITALY -------------------------------------------------------------------------------- 5. SOLE VOTING POWER: 176,070 NUMBER OF SHARES ------------------------------------------- BENEFICIALLY OWNED 6. SHARED VOTING POWER: 710,747,187 BY EACH REPORTING PERSON WITH: ------------------------------------------- 7. SOLE DISPOSITIVE POWER: 176,070 ------------------------------------------- 8. SHARED DISPOSITIVE POWER: 710,747,187 -------------------------------------------------------------------------------- 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON: 710,923,257 -------------------------------------------------------------------------------- 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) .... [ ] -------------------------------------------------------------------------------- 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9): 61.25% -------------------------------------------------------------------------------- 12. TYPE OF REPORTING PERSON (SEE INSTRUCTIONS): IN -------------------------------------------------------------------------------- Page 2 of 22 pages ------------------------ CUSIP NO. 88031 M 10 9 ------------------------ -------------------------------------------------------------------------------- 1. NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) ROCCA & PARTNERS S.A. -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [ ] (b) [ ] -------------------------------------------------------------------------------- 3. SEC USE ONLY -------------------------------------------------------------------------------- 4. CITIZENSHIP OR PLACE OF ORGANIZATION BRITISH VIRGIN ISLANDS -------------------------------------------------------------------------------- 5. SOLE VOTING POWER: NONE NUMBER OF SHARES ------------------------------------------- BENEFICIALLY OWNED 6. SHARED VOTING POWER: 710,923,257 BY EACH REPORTING PERSON WITH: ------------------------------------------- 7. SOLE DISPOSITIVE POWER: NONE ------------------------------------------- 8. SHARED DISPOSITIVE POWER: 710,923,257 -------------------------------------------------------------------------------- 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON: 710,923,257 -------------------------------------------------------------------------------- 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [ ] -------------------------------------------------------------------------------- 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9): 61.25% -------------------------------------------------------------------------------- 12. TYPE OF REPORTING PERSON (SEE INSTRUCTIONS): CO -------------------------------------------------------------------------------- Page 3 of 22 pages ------------------------ CUSIP NO. 88031 M 10 9 ------------------------ -------------------------------------------------------------------------------- 1. NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) SAN FAUSTIN N.V. -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [ ] (b) [ ] -------------------------------------------------------------------------------- 3. SEC USE ONLY -------------------------------------------------------------------------------- 4. CITIZENSHIP OR PLACE OF ORGANIZATION NETHERLANDS ANTILLES -------------------------------------------------------------------------------- 5. SOLE VOTING POWER: NONE NUMBER OF SHARES ------------------------------------------- BENEFICIALLY OWNED 6. SHARED VOTING POWER: 710,923,257 BY EACH REPORTING PERSON WITH: ------------------------------------------- 7. SOLE DISPOSITIVE POWER: NONE ------------------------------------------- 8. SHARED DISPOSITIVE POWER: 710,923,257 -------------------------------------------------------------------------------- 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON: 710,923,257 -------------------------------------------------------------------------------- 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [ ] -------------------------------------------------------------------------------- 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9): 61.25% -------------------------------------------------------------------------------- 12. TYPE OF REPORTING PERSON (SEE INSTRUCTIONS): CO -------------------------------------------------------------------------------- Page 4 of 22 pages ------------------------ CUSIP NO. 88031 M 10 9 ------------------------ -------------------------------------------------------------------------------- 1. NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) I.I.I. INDUSTRIAL INVESTMENTS INC. -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [ ] (b) [ ] -------------------------------------------------------------------------------- 3. SEC USE ONLY -------------------------------------------------------------------------------- 4. CITIZENSHIP OR PLACE OF ORGANIZATION BRITISH VIRGIN ISLANDS -------------------------------------------------------------------------------- 5. SOLE VOTING POWER: NONE NUMBER OF SHARES ------------------------------------------- BENEFICIALLY OWNED 6. SHARED VOTING POWER: 710,923,257 BY EACH REPORTING PERSON WITH: ------------------------------------------- 7. SOLE DISPOSITIVE POWER: NONE ------------------------------------------- 8. SHARED DISPOSITIVE POWER: 710,923,257 -------------------------------------------------------------------------------- 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON: 710,923,257 -------------------------------------------------------------------------------- 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [ ] -------------------------------------------------------------------------------- 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9): 61.25% -------------------------------------------------------------------------------- 12. TYPE OF REPORTING PERSON (SEE INSTRUCTIONS): CO -------------------------------------------------------------------------------- Page 5 of 22 pages ------------------------ CUSIP NO. 88031 M 10 9 ------------------------ -------------------------------------------------------------------------------- 1. NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) SIDERTUBES S.A. -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [ ] (b) [ ] -------------------------------------------------------------------------------- 3. SEC USE ONLY -------------------------------------------------------------------------------- 4. CITIZENSHIP OR PLACE OF ORGANIZATION LUXEMBOURG -------------------------------------------------------------------------------- 5. SOLE VOTING POWER: NONE NUMBER OF SHARES ------------------------------------------- BENEFICIALLY OWNED 6. SHARED VOTING POWER: 710,923,257 BY EACH REPORTING PERSON WITH: ------------------------------------------- 7. SOLE DISPOSITIVE POWER: NONE ------------------------------------------- 8. SHARED DISPOSITIVE POWER: 710,923,257 -------------------------------------------------------------------------------- 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON: 710,923,257 -------------------------------------------------------------------------------- 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [ ] -------------------------------------------------------------------------------- 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9): 61.25% -------------------------------------------------------------------------------- 12. TYPE OF REPORTING PERSON (SEE INSTRUCTIONS): CO -------------------------------------------------------------------------------- Page 6 of 22 pages Item 1. (a) Name of Issuer: Tenaris S.A. (b) Address of Issuer's Principal Executive Offices: 23, Avenue Monterey L-2163 Luxembourg Item 2. (a) Name of Person Filing: Roberto Rocca Rocca & Partners S.A. San Faustin N.V. I.I.I. Industrial Investments Inc. Sidertubes S.A. (b) Address of Principal Business Office or, if none, Residence: Roberto Rocca Av. Leandro N. Alem 1067, 29th floor Buenos Aires Argentina Rocca & Partners S.A. Vanterpool Plaza, 2nd Floor, Wickhams Cay I, Road Town, Tortola British Virgin Islands San Faustin N.V. Berg Arrarat 1 Curacao Netherlands Antilles I.I.I. Industrial Investments Inc. Vanterpool Plaza, 2nd Floor, Wickhams Cay I, Road Town British Virgin Islands Sidertubes S.A. 23 Avenue Monterey L-2086 Luxembourg Citizenship: See item 4 on page 2 See item 4 on page 3 See item 4 on page 4 See item 4 on page 5 See item 4 on page 6 (c) Title of Class of Securities: Ordinary Shares Page 7 of 22 pages (d) CUSIP Number: 88031 M 10 9 Item 3. If this statement is filed pursuant toss.ss.240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a: (Not Applicable) (a) [ ] Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o); (b) [ ] Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c); (c) [ ] Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c); (d) [ ] Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8); (e) [ ] An investment adviser in accordance with ss.240.13d-1(b)(1)(ii)(E); (f) [ ] An employee benefit plan or endowment fund in accordance with ss.240.13d-1(b)(1)(ii)(F); (g) [ ] A parent holding company or control person in accordance with ss.240.13d-1(b)(1)(ii)(G); (h) [ ] A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813); (i) [ ] A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3); (j) [ ] Group, in accordance withss.240.13d-1(b)(1)(ii)(J). Item 4. Ownership. Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1. (a) Amount beneficially owned: See item 9 on page 2 See item 9 on page 3 See item 9 on page 4 See item 9 on page 5 See item 9 on page 6 (b) Percent of class: See item 11 on page 2 See item 11 on page 3 See item 11 on page 4 See item 11 on page 5 See item 11 on page 6 (c) Number of shares as to which the person has: (i) Sole power to vote or to direct the vote: See item 5 on page 2 See item 5 on page 3 See item 5 on page 4 See item 5 on page 5 See item 5 on page 6 Page 8 of 22 pages (ii) Shared power to vote or to direct the vote: See item 6 on page 2 See item 6 on page 3 See item 6 on page 4 See item 6 on page 5 See item 6 on page 6 (iii) Sole power to dispose or to direct the disposition of: See item 7 on page 2 See item 7 on page 3 See item 7 on page 4 See item 7 on page 5 See item 7 on page 6 (iv) Shared power to dispose or to direct the disposition of: See item 8 on page 2 See item 8 on page 3 See item 8 on page 4 See item 8 on page 5 See item 8 on page 6 Page 9 of 22 pages Item 5. Ownership of Five Percent or Less of a Class. If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following [ ]. Not applicable. Item 6. Ownership of More than Five Percent on Behalf of Another Person. Not applicable. Item 7. Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company. See Exhibit A. Item 8. Identification and Classification of Members of the Group. Not applicable. Item 9. Notice of Dissolution of Group. Not applicable. Item 10. Certification. Not applicable. Page 10 of 22 pages SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by ROBERTO ROCCA to sign this statement, certify that the information set forth in this Schedule 13G is true, complete and correct. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Schedule 13G on his own behalf and on behalf of ROCCA & PARTNERS S.A., SAN FAUSTIN N.V., SIDERTUBES S.A. and I.I.I. INDUSTRIAL INVESTMENTS INC. January 23, 2003 /s/ Fernando Mantilla --------------------- Fernando Mantilla Attorney-in-fact Page 11 of 22 pages SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by ROCCA & PARTNERS S.A. to sign this statement, certify that the information set forth in this Schedule 13G is true, complete and correct. Pursuant to Rule 13d - 1(k)(1), the undersigned joins in the filing of this Schedule 13G on his own behalf and on behalf of Roberto ROCCA, SAN FAUSTIN N.V., SIDERTUBES S.A., I.I.I. INDUSTRIAL INVESTMENTS INC. January 23, 2003 /s/ Fernando Mantilla --------------------- Fernando Mantilla Attorney-in-fact Page 12 of 22 pages SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by SAN FAUSTIN N.V. to sign this statement, certify that the information set forth in this Schedule 13G is true, complete and correct. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Schedule 13G on his own behalf and on behalf of Roberto ROCCA, ROCCA & PARTNERS S.A., SIDERTUBES S.A., and I.I.I. INDUSTRIAL INVESTMENTS INC.. January 23, 2003 /s/ Fernando Mantilla --------------------- Fernando Mantilla Attorney-in-fact Page 13 of 22 pages SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by I.I.I. Industrial Investments Inc. to sign this statement, certify that the information set forth in this Schedule 13G is true, complete and correct. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Schedule 13G on his own behalf and on behalf of Roberto ROCCA, ROCCA & PARTNERS S.A., SAN FAUSTIN N.V., and SIDERTUBES S.A. January 23, 2003 /s/ Fernando Mantilla --------------------- Fernando Mantilla Attorney-in-fact Page 14 of 22 pages SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by SIDERTUBES S.A. to sign this statement, certify that the information set forth in this Schedule 13G is true, complete and correct. Pursuant to Rule 13d -1(k)(1), the undersigned joins in the filing of this Schedule 13G on his own behalf and on behalf of Roberto ROCCA, ROCCA & PARTNERS S.A., SAN FAUSTIN N.V. and I.I.I. INDUSTRIAL INVESTMENTS INC. January 23, 2003 /s/ Fernando Mantilla --------------------- Fernando Mantilla Attorney-in-fact Page 15 of 22 pages EXHIBIT INDEX Exhibit Description A Item 7 Information. B Power of Attorney for Roberto Rocca, dated January 17, 2003. C Power of Attorney for Rocca & Partners S.A., dated January 20, 2003. D Power of Attorney for San Faustin N.V., dated January 17, 2003. E Power of Attorney for I.I.I. Industrial Investments Inc., dated January 17, 2003. F Power of Attorney for Sidertubes S.A., dated January 17, 2003. Page 16 of 22 pages EXHIBIT A ITEM 7 INFORMATION Roberto Rocca controls a majority of the voting power of Rocca & Partners S.A. Roberto Rocca and Rocca & Partners share majority voting power over San Faustin N.V. Sidertubes S.A. is a wholly-owned subsidiary of I.I.I. Industrial Investments Inc., which is a wholly-owned subsidiary of San Faustin N.V. The shares of Tenaris S.A. to which this statement relates are held directly by Roberto Rocca, San Faustin N.V. and Sidertubes S.A. Page 17 of 22 pages EXHIBIT B [LETTERHEAD OF ROBERTO ROCCA] POWER OF ATTORNEY The undersigned, Roberto Rocca, an Italian citizen resident in the Argentine Republic, hereby constitutes and appoints Carlos Manuel Franck, Fernando R. Mantilla and Carlos E. Zandona, and each of them, as attorneys or attorney of the undersigned with full power of substitution and resubstitution, to sign on its behalf a Statement on Schedule 13G relating to the Common Stock, of TENARIS S.A., including any agreements attached as exhibits thereto, and to sign any or all amendments to such Statement, and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys or attorney, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, hereby ratifying and confirming all that said attorneys or attorney, or any of them or their substitute or substitutes, may lawfully do or cause to be done by virtue hereof. By: /s/ Roberto Rocca ----------------- Roberto Rocca Dated: January 17, 2003 Page 18 of 22 pages EXHIBIT C [LETTERHEAD OF ROCCA & PARTNERS S.A.] POWER OF ATTORNEY The undersigned, Roberto Rocca, President of ROCCA & PARTNERS, a company organized under the laws of the British Virgin Islands, hereby constitutes and appoints Carlos Manuel Franck, Fernando R. Mantilla and Carlos E. Zandona, and each of them, as attorneys or attorney of the undersigned with full power of substitution and resubstitution, to sign on its behalf a Statement on Schedule 13G relating to the Common Stock, of TENARIS S.A., including any agreements attached as exhibits thereto, and to sign any or all amendments to such Statement, and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys or attorney, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, hereby ratifying and confirming all that said attorneys or attorney, or any of them or their substitute or substitutes, may lawfully do or cause to be done by virtue hereof. By: /s/ Roberto Rocca ----------------- Roberto Rocca Dated: January 20, 2003 Page 19 of 22 pages EXHIBIT D [LETTERHEAD OF SAN FAUSTIN N.V.] POWER OF ATTORNEY The undersigned, Roberto Bonatti, President of SAN FAUSTIN N.V., a company organized under the laws of Curacao, hereby constitutes and appoints Carlos Manuel Franck, Fernando R. Mantilla and Carlos E. Zandona, and each of them, as attorneys or attorney of the undersigned with full power of substitution and resubstitution, to sign on its behalf a Statement on Schedule 13G relating to the Common Stock, of TENARIS S.A., including any agreements attached as exhibits thereto, and to sign any or all amendments to such Statement, and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys or attorney, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, hereby ratifying and confirming all that said attorneys or attorney, or any of them or their substitute or substitutes, may lawfully do or cause to be done by virtue hereof. By: /s/ Roberto Bonatti ------------------- Roberto Bonatti President Dated: January 17, 2003 Page 20 of 22 pages EXHIBIT E [LETTERHEAD OF I.I.I. INDUSTRIAL INVESTMENTS INC.] POWER OF ATTORNEY The undersigned, Roberto Bonatti, President of I.I.I. INDUSTRIAL INVESTMENTS Inc., a company organized under the laws of the British Virgin Islands, hereby constitutes and appoints Carlos Manuel Franck, Fernando R. Mantilla and Carlos E. Zandona, and each of them, as attorneys or attorney of the undersigned with full power of substitution and resubstitution, to sign on its behalf a Statement on Schedule 13G relating to the Common Stock, of TENARIS S.A., including any agreements attached as exhibits thereto, and to sign any or all amendments to such Statement, and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys or attorney, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, hereby ratifying and confirming all that said attorneys or attorney, or any of them or their substitute or substitutes, may lawfully do or cause to be done by virtue hereof. By: /s/ Roberto Bonatti ------------------- Roberto Bonatti President Dated: January 17, 2003 Page 21 of 22 pages EXHIBIT F [LETTERHEAD OF SIDERTUBES S.A.] POWER OF ATTORNEY The undersigned, Paolo Rocca, President of SIDERTUBES S.A., a company organized under the laws of Luxembourg, hereby constitutes and appoints Carlos Manuel Franck, Fernando R. Mantilla and Carlos E. Zandona, and each of them, as attorneys or attorney of the undersigned with full power of substitution and resubstitution, to sign on its behalf a Statement on Schedule 13G relating to the Common Stock, of TENARIS S.A., including any agreements attached as exhibits thereto, and to sign any or all amendments to such Statement, and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys or attorney, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, hereby ratifying and confirming all that said attorneys or attorney, or any of them or their substitute or substitutes, may lawfully do or cause to be done by virtue hereof. By: /s/ Paolo Rocca --------------- Paolo Rocca President Dated: January 17, 2003 Page 22 of 22 pages