The clinical features of 34 patients with Burkitt's lymphoma diagnosed at the American University Medical Center (AUMC) are described. Ages ranged between 3 and 20 years (median, 7 years). Seventy-three percent of the patients were younger than 8 years. Three cases occurred among siblings. The primary site of disease at presentation was the abdomen, 23 patients; jaw, 6; jaw and abdomen, 2; Waldeyer's ring, 2; and mediastinum, 1. Of those who had abdominal disease, the involvement was diffuse and extensive in abdomen and pelvis in 9, apparently confined to the ileocecal region in 5, mesenteric nodes and small intestine in 5, large intestine in 1, and ovary in 3. One patient presented with paraplegia. The bone marrow was studied in 19 patients; it was positive in 5 and suspicious in 2. None had frank leukemia. CSF was studied in 4 patients at presentation and was negative. Eight patients developed meningeal lymphoma during the course of the disease. Liver involvement was documented in 3 patients. Peripheral lymphadenopathy was observed at presentation in 11 patients (9, neck; 2, inguinal + axillary). In contrast to African Burkitt's, the majority of our patients presented with abdominal disease, and in contrast to the American form, our patients were younger with a median age similar to that of African Burkitt's. Thirty percent of the patients had jaw tumor at presentation--a figure intermediate between the African and the American Burkitt's.