Diarrhoeal stools from patients, and river/estuarine water, crab and shrimp samples from the environment of Ikom and Calabar areas of Nigeria were examined bacteriologically for Vibrio spp. Vibrio cell populations were additionally enumerated in the environmental samples. Three Vibrio species were isolated: Vibrio cholerae and V. parahaemolyticus from both the clinical and the environmental samples, and V. alginolyticus from the latter only. Vibrio cholerae was the major cause of Vibrio diarrhoea in the region and was confirmed as the major aetiologic agent in the cholera outbreak in Ikom. Clinical disease by V. parahaemolyticus was confirmed and was indistinguishable from V. cholerae symptoms except in severity and fever, which occurred in some of the latter. V. parahaemolyticus was isolated more frequently (48.8%), particularly from the environment, than V. cholerae (36.6%) and V. alginolyticus (0.78%). The log10 Vibrio cell count of the three species followed a similar pattern (2.42 ± 2.47-5.07 ± 5.00, 1.96 ± 2.27-5.01 ± 5.14, and 2.78 ± 3.21 cfu, respectively). There was higher incidence of the Vibrio species in the dry season (23.3-93.3%) than in the rainy season (3.3-70.0%). The Vibrio cell count followed similar seasonal variation (1.94 ± 2.37-5.32 ± 5.59 cfu in the dry season and 1.96 ± 1.03-4.67 ± 5.01 cfu in the rainy season).