1. A case of acute hemolytic anemia with hemoglobinuria precipitated by sulfadiazine is described.
2. Spherocytosis and increased hypotonic saline fragility were demonstrated during the acute phase of the disease.
3. Abnormal hemagglutinins and hemolysins were not present in the patient's serum.
4. The significance of these findings as related to the etiology of the disease is discussed.