CONTEXT: Traveler's diarrhea (TD) can incapacitate travelers. Characteristics of TD could be helpful in identifying individuals who might benefit from a vaccine against TD. OBJECTIVE: To determine epidemiology, etiology, and impact of TD in Jamaica. Design Two-armed, cross-sectional survey conducted between March 1996 and May 1997. SETTING: Sangster International Airport and 10 hotels in Montego Bay area, Jamaica. SUBJECTS: To investigate epidemiology and impact, 30369 short-term visitors completed a questionnaire just before boarding their homebound aircrafts. To investigate etiology, 322 patients (hotel guests) with TD provided stool samples. MAIN OUTCOME MEASURES: Attack and incidence rates of reported diarrhea and of classically defined TD (> or =3 unformed stool samples in 24 hours and > or =1 accompanying symptom), incapacity, risk factors, and etiology. RESULTS: The attack rate for diarrhea was 23.6% overall, with 11.7% having classically defined TD. For a mean duration of stay of 4 to 7 days, the incidence rate was 20.9% (all TD) and 10.0% (classic TD). Among airport respondents, the incapacity lasted a mean of 11.6 hours. Less than 3% of all travelers avoided potentially high-risk food and beverages. The most frequently detected pathogens were enterotoxigenic Escherichia coli, Rotavirus, and Salmonella species. CONCLUSIONS: A realistic plan for reducing TD is needed. Preventive measures such as the improvement of hygienic conditions at the destination, and/or the development of vaccines against the most frequent pathogens associated with TD may contribute toward achieving this goal.