Hodgkin's disease is a malignancy which can be cured even in advanced stages. Patients who have survived this illness, however, are at risk for developing a second malignant disorder. Several factors, including treatment itself, influence the risk of developing the secondary cancers. The patient's age at the time of treatment, however, is the most significant factor relating to second-cancer risk. With the exception of thyroid carcinomas, sarcomas, and probably breast cancer, which are most clearly increased in patients treated with radiotherapy during childhood or adolescence, the risk for any second malignancy, including myelogenous leukemia, rises when patients are treated at the age of 40 years or more.