The purpose of this study was to identify the enteropathogens causing acute diarrheal disease in Americans living in the North Africa/Middle East region during a 34-month period from February 12, 1985 to December 30, 1987 to guide preventive and therapeutic measures. Stool specimens were examined and an epidemiologic questionnaire was administered to patients with acute diarrhea at the Outpatient Health Unit of the United States Embassy in Cairo, Egypt. The subjects consisted of 126 American employees and dependents of the U. S. Embassy in Cairo, Egypt with diarrhea of less than two weeks duration. Subjects received routine medical care administered by the U.S. Embassy Medical staff. A possible etiologic agent was detected in 41% of the subjects. Enteroadherent Escherichia coli was the most commonly isolated enteropathogen. A high degree of antimicrobial resistance was noted among the bacterial isolates. but all were susceptible to the quinolone antibiotics. Episodes of acute diarrhea occurring among American expatriates in Cairo, Egypt were primarily of bacterial etiology, but only a small portion were caused by the bacterial pathogens routinely identified in a standard clinical bacteriology laboratory. Most of the diarrheal episodes were due to noninvasive enteroadherent E. coli that may cause prolonged disease requiring antimicrobial therapy.