The authors in this study report the incidence and risk factors associated with the development of solid tumors in 4349 pediatric and adult patients who underwent allogeneic stem cell transplant (SCT) for acute myelogenous leukemia (AML) in CR1 or chronic myelogenous leukemia (CML) in first chronic phase. All subjects received chemotherapy only conditioning regimens with busulfan and cyclophosphamide. The median time of follow-up for survivors was 8.2 years; 47% of patients were alive and evaluable at 5 years after SCT and 18% were alive and evaluable at 10 years after SCT. Sixty-six solid cancers were reported; the cumulative incidence of solid tumors at 3, 5 and 10 years after SCT were 0.7, 0.9, and 2.0% for AML patients and 0.5, 1.1, and 3.4% for CML patients. These rates were higher than expected rates in the general population. . On Cox-regression analysis, risk factors for developing solid tumors included older age, chronic GVHD and use of peripheral blood (as opposed to bone marrow) as a stem cell source.