Efforts were made to serotype the Vibrio anguillarum strains isolated from fish in Taiwan from 1976 to 1986. Included were 100 strains from milkfish (Chanos chanos), 10 from ayu (Plecoglossus altivelis), 1 from tiger shrimp (Penaeus monodon) and 8 from culture environments. Seven distinct serotypes (T-O-I through T-O-VII) were established from these 119 strains of V. anguillarum examined on the basis of agglutination test with thermostable (O) antigens. Eighty-five strains isolated from milkfish and 5 strains from ayu belonged to serotype T-O-I which appeared to be dominant. However, serotypes II, III, IV, V, VI and VII only occurred sporadically. Besides these, 9 strains isolated from milkfish and 1 from pond water were found to be nontypable. V. anguillarum strains PT213, LS174 and ITAL72 belong to our serotype T-O-I, ATCC19264 (NCMB6), PT24. and SG7701 to our serotype T-O-V and strain PT493 to our serotype T-O-VI.