The successful development of allogeneic bone marrow transplantation (BMT) has markedly improved the treatment results for acute leukemia and other hematologic diseases. However, significant complications are associated with this procedure including the development of chronic graft versus host disease (GVHD). Treatment for this condition requires chronic immunosuppression which can lead to the development of second cancers. It is well known that immunosuppression is associated with a variety of tumors, most commonly lymphoma. The development of solid tumors appears to be less common but follow-up studies of patients treated for Hodgkin's disease demonstrate a rising incidence of solid tumor development after a delay of 5 to 10 years. We describe a patient recently treated for a squamous cell carcinoma of the esophagus which developed 5 years after an allogeneic BMT for acute myelogenous leukemia (AML). The patient had been treated with immunosuppressants for chronic GVHD. The clinical course is described and the literature is reviewed regarding recent experience with the development of solid tumors following allogeneic BMT. The majority of second tumors following BMT are lymphomas and leukemias. Secondary solid tumors are less common, but the incidence appears to increase over time. Squamous carcinomas are most common and a preparative regimen combining radiation and chemotherapy may increase risk. Careful long-term follow-up of BMT is essential in order to detect second tumors at an early stage.