To better understand the epidemiology of diarrhea in deployed personnel to the Middle East, a prospective cohort study of travelers' diarrhea (TD) was conducted between May 2004 and January 2005 at the Multinational Force and Observers (MFO) camp in the southern Sinai. A baseline entry questionnaire and stool specimen was provided on study entry, and volunteers were followed every 6 weeks. Of 211 volunteers, 145 (68.7%) completed one or more follow-up visits. In total, 416 follow-up surveys were completed, which described an overall incidence of 25.2 episodes per 100 person months (95% confidence interval = 21.2-30.0). Additionally, stools were collected in 72 of 77 diarrhea-associated clinic visits, with bacterial pathogens most commonly isolated (enterotoxigenic Escherichia coli in 30 [42%] samples and Campylobacter jejuni in 7 [10%] samples) Despite modern preventive methods, diarrhea is still a common problem for deployed US military personnel in Egypt, frequently resulting in diminished ability to work.