Fifty percent of the tropical fish in a local freshwater aquarium died during a three week period. Vibrio spp. was isolated from two fish submitted. Gross signs of hyperemia and microscopic evidence of haemorrhage and congestion were the main lesions. The isolated bacterium closely resembled V. anguillarum. Its cultural characteristics were compared with those of three known isolates of V. anguillarum, and its pathogenicity for selected species of freshwater fishes and laboratory mammals was studied.