Intestinal protozoa are one of the leading causes of waterborne outbreaks. Stool samples of 196 residents from a village of Izmir, using the public water supply, were collected during an outbreak of gastroenteritis. Patients were asked to fill out a questionnaire reporting on gender, age, gastrointestinal symptoms, whether or not there was a toilet in the house, their hygiene practices, and similar symptoms in the household members. Of the patients who had gastrointestinal symptoms (74.5%), diarrhea was observed in 69.5% whereas bloody and mucoid stools were observed in 20.4 %. The stool samples were examined for intestinal parasites by wet mount and trichrome stain and were also cultured in the Robinson medium. Pathogenic parasites were detected in 11 samples (5.6%) as follows: Giardia intestinalis in 7, Hymenolepis nana in 1 and Blastocystis hominis in 4. Entamoeba histolytica/dispar was not detected by direct wet mount in any of 8 patients who had E. histolytica/E. dispar in culture whereas it was detected in the trichrome stained slides of 3 patients. Amoeba prevalence in the 15-44 age-group was significantly high when compared with the 0-14 age group. The prevalence of pathogenic parasites was high among the people who had a toilet outdoors. Drinking water was thought to be a principal source of this outbreak.