To determine the source and extent of an outbreak of Vibrio cholerae 0139 Bengal infections among 630 cruise ship passengers to Southeast Asia, a retrospective cohort study was done. Questionnaires were sent to all passengers from the United States, Canada, and the United Kingdom, and serum samples were requested from all passengers reporting diarrhea. A case was defined as diarrheal illness with onset between 8 and 28 February 1994 and a cholera antitoxic antibody titer ≥800. Six passengers, including 1 with bacteremia, met the case definition. Illness was associated with eating yellowrice at a buffet restaurant in Bangkok on 10 February (relative risk undefined, P =.005). This international outbreak demonstrates foodborne transmission of Vibrio cholerae0139 Bengal, an emerging cause of epidemic cholera in Asia, to tourists from Western countries. Physicians should suspect infection with either V. cholerae 01 or 0139 in any patient with severe watery diarrhea after travel to the developing world.