Exhibit 21 THERMO FIBERTEK INC. Subsidiaries of the Registrant At February 28, 1999, the Registrant owned the following companies: STATE OR REGISTRANT'S JURISDICTION OF PERCENT OF NAME INCORPORATION OWNERSHIP - ---------------------------------------------------------------------------------------------------------------- AES Equipos y Sistemas S.A. de C.V. Mexico 100 Fibertek Construction Company, Inc. Maine 100 Thermo AES Canada Inc. Canada 100 Thermo Black Clawson Inc. Delaware 100 Thermo Black Clawson (China) China 100 Thermo Black Clawson S.A. France 100 Thermo Fibertek Holdings Limited United Kingdom 100 Thermo Black Clawson Limited United Kingdom 100 Thermo Fibertek U.K. Limited United Kingdom 100 Vickerys Holdings Limited United Kingdom 100 Vickerys Limited United Kingdom 100 Winterburn Limited United Kingdom 100 Thermo Web Systems, Inc. Massachusetts 100 Fiberprep Inc. Delaware 95 (31.05% of which shares are owned directly by E. & M. Lamort, S.A.) Fiberprep Securities Corporation Delaware 100 Thermo Fibergen Inc. Delaware 70.81* (additionally, 1.81%* of the shares are owned directly by The Thermo Electron Companies Inc.) Fibergen Securities Corporation Massachusetts 100 GranTek Inc. Wisconsin 100 TMO Lamort Holdings Inc. Delaware 100 E. & M. Lamort, S.A. France 100 Lamort-Black Clawson Industrial Ltda. Brazil 70 Lamort GmbH Germany 100 Lamort Iberia S.A. Spain 100 Lamort Italia S.R.L. Italy 100 Lamort Paper Services Ltd. United Kingdom 100 Nordiska Lamort Lodding AB Sweden 100 * As of January 2, 1999