Cytogenetic abnormalities have been reported in lymphoproliferative disorders, the most common of which is the t(8;14) translocation in Burkitt and Burkitt-like lymphomas. We report a 30-year-old homosexual male with Burkitt-like lymphoma and trisomy 12. This patient presented with persistent generalized lymphadenopathy and subsequently developed advanced lymphoma. Cell surface markers revealed a monoclonal pattern containing mu heavy chain and kappa light chain immunoglobulins. Cytogenetic analysis of bone marrow involved with lymphoma revealed an additional chromosome #12. Mitogen-stimulated cultures of peripheral blood showed a normal 46,XY karyotype. Trisomy 12 has been found in chronic lymphocytic leukemia and in other low-grade B-cell lymphoproliferative disorders, but not in Burkitt-like lymphoma.