<PAGE>
 
                                                                      EXHIBIT 21
 
                                 TUBOSCOPE INC.
                               DECEMBER 31, 1997
 
Tuboscope Inc. (US--Delaware)
  Gauthier Brothers Rentals, Inc. (U.S.Calif.)
  Tuboscope Vetco International Inc. (US--Texas)
    Tuboscope Vetco International Inc. (Colombia) branch
    Tuboscope Vetco do Brasil Equipamentos e Servicos Ltda (Brazil)
    Tuboscope Vetco (Thailand) Ltd.
    Tuboscope Vetco Moscow Ltd. (Russia)
    Tuboscope Vetco Export Sales Corp (FSC--Barbados)
    Tuboscope Vetco Services (Panama) Inc.
      Tuboscope Vetco Services (Panama) Inc.--Abu Dhabi branch
      Tuboscope Vetco Services (Panama) Inc.--Kuwait branch
      Tuboscope Vetco Services (Panama) Inc.--Singapore branch
      Tuboscope Vetco (Nigeria) Ltd. (40%)
      Italiana Partecipazioni s.r.l. (95%)
              Italiana lspezioni s.r.l. (95%)
    Tuboscope Overseas Corp. S.A. (Switzerland)
    Vetco Enterprise AG (Switzerland)
      Tuboscope Vetco Osterreich GmbH (Austria)
      Vetco Saudi Arabia Ltd. (P/S--45% Stock)
      Tuboscope Vetco (Deutschland) GmbH (Germany)
              Tuboscope Vetco (Deutschland) GmbH (Germany)--Bahrain branch
              Tuboscope Vetco (Deutschland) GmbH (Germany)--Tunisia branch
              Tuboscope Vetco (Deutschland) GmbH (Germany)--Italy branch
              Tuboscope Vetco (Deutschland) GmbH (Germany)--France branch
              Tuboscope Vetco (Deutschland) GmbH (Germany)--Oman branch
              Tuboscope Vetco (Deutschland) GmbH (Germany)--Netherlands branch
              Tuboscope Vetco (Deutschland) GmbH (Germany)--Nigeria branch
              Tuboscope Vetco (Deutschland) GmbH (Germany)--Egypt branch
              Tuboscope Vetco (Deutschland) GmbH (Germany)--Pakistan branch
              Tuboscope Vetch Technology GmbH (Germany)
                 Tuboscope Vetco Technology GmbH (Germany)--Italy branch
                 Tuboscope Vetco Technology GmbH (Germany)--Spain branch
                 Tuboscope Vetco Technology GmbH (Germany)--Indonesia branch
                 Tuboscope Vetco Technology GmbH (Germany)--Russian branch
                 Tuboscope Vetco (Brunei) SDN.BDH (49%)
              Vetco Abu Dhabi (P/S--United Arab Emirates)
                 Vetco Coating GmbH (Germany)
    Tuboscope Vetco de Argentina, S.A. (Argentina)
    TVI Inspecciones de Venezuela, C.A. (Venezuela)
    Tuboscope Vetco Canada Inc. (Canada)
      Tuboscope Pipeline Services Canada Inc. (Canada)
              Italiana Partecipazioni s.r.l. (5%)
      Tuboscope Vetco Far East Pte Ltd. (Singapore)
              Pesaka Inspection Services SDN.BHD (49%-Malaysia)
              Tuboscope Vetco Far East Pte Ltd.--Phillippines branch
              Tuboscope Vetco Far East Pte Ltd.--Australia branch
              Italiana Ispezioni s.r.l. (5%)
    Tuboscope Pipeline Services Inc. (US--Texas)
<PAGE>
 
                                                          EXHIBIT 21 (CONTINUED)
 
      Vetco Pipeline Services Inc. (US--Texas)
      Vetco Pipeline Services Ltd. (Canada)
      Tuboscope Vetco Pipeline Services S.A. de C.V. (Mexico)
    Remediation Management Services, LLC
  Tubo-FGS Inc. (Del.)
  Fiberglass Systems Holdings Inc. Del.
    Fiberglass Systems LLP.
    Star Composites International LTD. (Virgin Isles)
  Tuboscope (Holding US) Inc. Del. U.S.
      Wadeco Oilfield Services Ltd. (Canada)
              Wadeco Inc. (US--North Dakota)
    Vetco Inspection Norge A.S. (Norway)
    Tuboscope Vetco Norge A.S..
    Tuboscope Vetco (France) S.A.
    Texas Oil Tools Inc. (US Nevada)
    Tuboscope MECL (Trinidad) Ltd. (50% P/S)
    Tube-Kote Inc. dba Tuboscope Vetco International Oilfield Services
    (US--Texas)
  Hydra Rig, Inc. (US--Texas)
  Environmental Procedures, Inc. (US--Delaware)
    Environmental Procedures P.T.E. Ltd. (Singapore)
    Environmental Procedures, Inc. (US-Delaware)--Ecuador branch
    Advanced Wirecloth, Inc. (US--Louisiana)
    Tuboscope S.A. de CV (Mexico)
    Environmental Procedures (US--Texas)--Colombia branch
  Drexel Oilfield Services BDN (Malaysia)
  Drexel Oilfield Services PTE Ltd. (Singapore)
  Drexel Equipment A/S (Norway)
  Drexel Oilfield Services, Ltd. (Bermuda)
    Drexel Oilfield Services, LLC (49%--Dubai)
    Venezuela Well Analysis, S.A. (Venezuela)
    Brandt Company de Argentina S.A. (Argentina)
    Screen Manufacturing Company, Ltd. (Trinidad)
    Venwell International, Inc. (US--Texas)
      Venwell International, Inc. (US--Texas)--Trinidad branch
    Drexel Oilfield Services s.r.l. Italy 95%
  Tuboscope IP Inc. (US Del.)
  Tuboscope Holdings Ltd. (UK)
    Chargewood Limited
    Enaco Mudcat Systems Ltd.
      Enaco Plc.
      Pump Systems Ltd.
      Cut-Rite Tubular Services Ltd.
      Tulsa Equipment Manufacturing Company
      Tuboscope Services de Bolivia S.A.
      American Rodco Inc. (10%)
    Pressure Control Engineering Ltd. (UK)
    SSR Ltd. (UK)
      SSR (Norway)
    Drexel Equipment (UK) Ltd.
      The Brandt Company (UK) Ltd.
<PAGE>
 
                                                          EXHIBIT 21 (CONTINUED)
 
      Environmental Procedures (UK) Limited
      Tuboscope Pipeline Services Ltd. (UK)
              Tuboscope Vetco (UK) Ltd.
              Linalog Ltd. (UK)
              Tuboscope Vetco Capital Ltd. (Scotland)