Esterases and lactate-(LDH) and L-malate-(MDH) dehydrogenases of 64 strains of 13 species of Flavobacterium (particularly 46 strains of F. meningosepticum belonging to 15 different serotypes) were analyzed by horizontal polyacrylamide-agarose gel electrophoresis. Twenty-five esterase types were detected; these enzymes were distinguished by their spectra of hydrolytic activity towards five synthetic substrates (hydrolytic type) and their electrolytic mobilities (electrophoretic type). No variant of LDH was detected in all the strains of Flavobacterium. No variant of MDH was detected in three species: F. aquatile, F. branchiophilum, and F. breve and in serotype I, J and L. of F. meningosepticum. These results within the genus Flavobacterium permit precise identification, which may be useful for characterization of strains kept in collections as well as for epidemiological studies.