The incidence and etiological factors of diarrheal disease in 100 Egyptian village children were observed for one year. There were on the average 2.8 separate episodes of diarrhea per subject. Five children suffered no attacks. Thirty-five per cent of the diarrheal episodes were associated with Shigella isolation, while E. histolytica, although highly prevalent, did not show a close correlation with diarrheal disease incidence. This was also true for other intestinal parasites. Evidence is presented which indicates lack of firm or long-lasting clinical immunity to diarrheal disease caused by Shigella. A revision of clinical nomenclature in shigellosis is needed.