Fifty-six long-term survivors of bone marrow allografts were followed for a minimum of 40 months after bone marrow transplantation (BMT) to determine the frequency of secondary malignancies. The 56 patients included ten with severe aplastic anemia (SAA), 16 with acute myeloblastic leukemia (AML), 11 with acute lymphoblastic leukemia (ALL), and 19 with chronic myelogenous leukemia (CML). All patients received a preparative regimen combining high-dose chemotherapy with total body irradiation (TBI). Three patients developed a malignancy of the skin or oral mucosa. Two were diagnosed as squamous cell carcinoma and one as a malignant melanoma. All three patients had chronic graft versus host disease (GvHD) and were treated for prolonged periods with immunosuppressive medications. The lesions of all patients developed in areas involved by chronic GvHD.