A search for a canine reservoir of Vibrio cholerae was made in Calcutta, India. Over 500 dogs were examined bacteriologically; of these approximately one-third were also studied serologically. No evidence for a V. cholerae reservoir was found, although 14% of dogs harbored non-cholera vibrios in their intestines. Identical serotypes of these organisms were isolated from dogs, crows, and humans in the same geographical area. These results indicate that nonhuman reservoirs exist for non-cholera vibrios, in contrast to V. cholerae, and that these reservoirs may serve as sources of infections in humans.