A review of the Memorial Sloan-Kettering Cancer Center experience with second malignancies (SM) after childhood Hodgkin's Disease (HD) identified 17 SM in 320 patients who survived more than 1 year from, and were 15 years old or younger at the time of, HD diagnosis (1949 to 1983). Of 254 previously untreated patients, 12 SM were noticed as compared with 0.606 expected on the basis of rates in the general pediatric population (relative risk, 19.8; 95% confidence interval, 10.2 to 34.6). For patients who received multi-agent chemotherapy, the cumulative probability of developing acute nonlymphocytic leukemia (ANLL) or bone sarcoma was 6.2% and 5.5%, respectively, at 10 years from the initiation of therapy; the cumulative risk of all SM in this group reached 18.7% at 15 years. For patients who received radiation alone or with single-agent chemotherapy, the cumulative risk of SM rose from 0% at 10 years and 2% at 15 years, to 10.7% at 25 years from the initiation of treatment. The risk of ANLL after childhood HD was highest in the first 5 to 10 years after combined modality treatment, and aggressive forms of NHL were associated with excessive immunosuppression. Bone sarcomas predominated in solid SM in the first decade after HD treatment, whereas "adult-type" cancers, for example, breast and colon carcinomas, were more delayed. Our findings, supported by a literature review, point to a therapy-related enhanced risk of approximately age-appropriate solid SM. This possibility mandates careful surveillance of long-term survivors of childhood HD.