Among 345 patients with Hodgkin's disease (HD) in full remission and followed for a mean of 7.2 years (11 months-26 years) since the initial diagnosis, 33 were found to have a second malignancy. The cumulative incidence after 10 years was 13.5%, after 15 years 21%. Non-Hodgkin lymphoma was the most frequent (n = 7), followed by bronchial carcinoma (n = 5) and acute myeloid leukaemia (n = 3). There was a definitely increased risk in elder patients (P < 0.001) and in those who had had a splenectomy. There was no demonstrable effect of type of therapy, primary stage and frequency of recurrence. It is concluded that patients with Hodgkin's disease should have life-long oncological follow-up. This preliminary study is being extended into a multicentre investigation of a larger number of patients.