From January 1974 to September 1991, 245 consecutive patients with severe aplastic anemia underwent bone marrow transplantation at the Hôpital Saint-Louis, Paris, France. Five cases of solid tumor were observed overall, a number that leads to an 8-year cumulative incidence rate of 7.7% (95% CL: 0.9%, 14.5%). Relative to the general population, the risk was equal to 22 (95% CL: 7, 51; p < 0.001). The present report focuses on the unusual clinical course of patients developing malignant tumors after bone marrow transplantation for severe aplastic anemia. It also aims at reporting the difficulty encountered in comparing data from different sources.