The pathogenicity of V. coli for conventional swine was studied by inoculating pigs with cultures of V. coli and V. coli infected gut of gnotobiotic pigs. Thus, six conventional pigs were inoculated with strains of V. coli freshly isolated from infected gnotobiotic pigs. The cultures were grown in simulated sows milk, and added to the feed. Two other groups, of three pigs each, were infected by administration of minced intestine from two gnotobiotic pigs, heavily infected with the organism. Vibrio was isolated from all pigs, including five of the six controls, but larger numbers were isolated from the inoculated groups, especially from those fed macerated gut. Clinical signs of disease were not observed.