We have retrospectively analyzed the characteristics of 24 adult patients affected with non-endemic Burkitt's lymphoma (BL) and Burkitt cell acute leukemia (L3 ALL). The median age of the entire group was 29 years with a male preponderance (75%). Median LDH value was 580 mU/mL. Test for HIV-antibodies was carried-out in 16 patients; 5 of them (21%) showed HIV positive. CNS was involved in 25% of patients at diagnosis. In all cases studied for karyotype, the t(8;14) translocation was evident. As to therapy, 5 patients were not evaluable for early death, 12 were given an intensive ALL program, 5 a cyclic chemotherapy and 2 a new protocol alternating high-dose cyclophosphamide, high-dose cytarabine with mitoxantrone and the CHOP regimen. The overall complete remission rate was 42%; among 7 remitters, 4 have relapsed so far within a median time of 6 months. Three of 13 (23%) patients with lymphoma presentation are long remitters and may be cured; all cases had stage II disease and low LDH at diagnosis (less than 250 mU/mL). No patients with Burkitt's leukemia survive. CNS disease (8 cases) and septic shock (6 cases) were the most frequent terminal events. In our experience, the prognosis of advanced stage BL and L3 ALL in adults does remain dismal; the high prevalence of CNS disease and HIV-positivity may have contributed to the poor outcome.