In August 1988, a study was conducted to determine the etiology and risk factors associated with travelers' diarrhea among U.S. military personnel after a 5-day port visit to Alexandria, Egypt. Twenty-one percent of the 2,747 evaluated crew members of the USS John F. Kennedy reported an episode of acute diarrhea, which led to 155 sick-call visits and at least 110 lost man-days. The most common pathogen identified was enterotoxigenic Escherichia coli, and all isolated bacterial enteropathogens were sensitive to quinolone drugs. Independent risk factors for the development of diarrhea included: (1) consuming any meal ashore and specifically eating meats, desserts, or a buffet meal; and (2) a recent history of travelers' diarrhea. These data indicate that even brief port visits to developing countries pose a major threat to the health of U.S. shipboard personnel.