SUNIXARY. Esterases of strains of Vibrio cholerae, V . parahuemolyticus, noncholera and marine vibrios were examined by electrophoresis in starch gels. The enzyme patterns indicated a relative homogeneity occurring amongst the strains. No separation of the genus Vibrio into subgroups corresponding t o the E l Tor, classical cholera or noncholera groupings was noted. Overall deoxyribonucleic acid base composition for the Vibrio spp. ranged from 44-49 mol% guanine + cytosine, with the marine vibrios lowest in guanine $-cytosine content. Enzyme patterns for cholera vibrios isolated during very recent epidemics were identical to those of established laboratory strains, suggesting a marked stability of the esterase system for V . cholerae.