Therapy-related myelodysplastic syndrome/acute myeloid leukemia (t-MDS/AML) is a long-term complication of pediatric cancer. We retrospectively studied pediatric t-MDS/AML patients treated at MD Anderson from 1975 to 2007. We also compared those patients to pediatric patients with de novo MDS/AML during this time interval. Among 2589 children with cancer treated at MD Anderson, we identified 22 patients with t-MDS/AML. Patients with t-MDS/AML had a median age of 14 years. There was a male and Hispanic predominance. The most common primary malignancies were osteosarcoma and Hodgkin lymphoma. The median latency period was 4.1 years. Three patients received supportive care only. Group 1 (n=5) underwent stem cell transplantation without induction chemotherapy. Group 2 (n=5) patients received AML-type chemotherapy and a stem cell transplant postremission (n=5). Group 3 (n=4) received a stem cell transplant as salvage therapy. The respective 2-year survival rates for groups 1, 2, and 3 were 20%, 40%, and 25% (P=0.85). Patients with de novo AML were younger (P=0.001) and higher rates of complete remission (P=0.03), and survival (P<0.0001). Independent factors predicting shorter survival were poor/intermediate-risk cytogenetics (P=0.01), lower hemoglobin level (P=0.0001), and t-MDS/AML (vs. de novo) (P=0.003). Childhood t-MDS/AML has a poor prognosis. Although patients benefited from AML-type induction chemotherapy followed by stem cell transplantation as postremission therapy, effective therapies, and prevention are needed.