A retrospective study was conducted of 35 children in whom Dientamoeba fragilis was the only parasite found in the gastrointestinal (GI) tract. Gastrointestinal symptoms were present in 32 (91%) of these children; diarrhea was the most common finding in patients with acute symptoms, whereas abdominal pain was more common in children with chronic symptoms. Peripheral eosinophilia was present in half of the children examined and was statistically more significant in patients with D fragilis than in a control group of children admitted for elective surgery. Therapy with diiodohydroxyquin or metronidazole was effective; children's symptoms were diminished or were eliminated on follow-up evaluation after treatment. From this association between therapy and symptomatic relief, D fragilis should be considered pathogenic in those children with GI symptoms.