The incidence of diarrhea associated with infection by Vibrio species was investigated among attendees at the 1986 Interscience Conference on Antimicrobial Agents and Chemotherapy held in New Orleans. Twelve percent of respondents reported diarrhea; the risk of diarrhea was significantly higher in those who ate raw or cooked oysters (relative risk = 1.5, P = .005). At least one Vibrio species was recovered from 51 (11%) of 479 persons submitting stool specimens; however, only 15 (29%) of those with a positive stool culture also reported diarrhea. Of the five Vibrio species identified, V. parahaemolyticus was most common and was most strongly associated with diarrhea. V. cholerae serogroup O1 was not isolated despite the occurrence of a cholera outbreak during the same time period in Louisiana. Cultures of raw and cooked seafood served in local restaurants yielded five different Vibrio species. Although asymptomatic passage of Vibrio organisms was common among persons eating seafood, the risk of Vibrio gastroenteritis was low.