A total of 100 patients with American Burkitt's lymphoma (AMBL) (mean age, 15 years; M:F ratio 3:1; 3% black) have been treated at the National Cancer Institute since 1964. Eighteen of these had jaw involvement, 16 at presentation and 2 at relapse (mean age, 16 years; M:F ratio 1.6:1). None of these 18 patients was black. Of the 16 patients presenting initially with jaw tumors, 14 were first evaluated by their dentist; 8 were 16 years of age or older (adults) and 6 were younger than 16 years of age (children). Toothache and perioral numbness were the most frequent findings in adults, whereas toothache, loose teeth, intra-oral and extra-oral swelling were the most common complaints in children. Ten patients were treated with antibiotic therapy and/or dental extractions for presumed tooth infection. The distribution of jaw lesions was: unilateral mandibular (7), unilateral maxillary (4), bilateral mandibular (5), and four quadrants (2). Radiologic evaluation was abnormal in all 17 cases evaluated. Only three patients (all children) had disease limited to the jaw. Four of eight children and 3 of 10 adults are long-term survivors with a median follow-up of seven years (range, 2-15 years). American Burkitt's lymphoma with jaw involvement differs from African Burkitt's lymphoma (AFBL) with jaw involvement in a number of ways: (1) the incidence of jaw tumors in adults is similar to that in children; (2) the incidence of jaw tumors is not greater in males; (3) tumor is considerably more limited in extent with a single quadrant mandibular lesion being the most common presentation; and (4) clinical presentation also differs, with toothache and perioral numbness, uncommon in AFBL, being the most frequent complaints. These marked differences in the frequency and clinical characteristics of jaw tumor of AMBL and AFBL are consistent with other findings indicating that these diseases may differ phenotypically.