A consecutive series of 2,999 patients, diagnosed with Hodgkin's disease (HD) between 1950 and 1979, was assembled from the records of the Birmingham and West Midlands Cancer Registry and followed to the end of 1984. Cohort analyses of subsequent primary cancers among 1,976 patients, surviving one or more years (mean follow-up 6.7 person-years), were carried out in relation to overall treatment by radiotherapy (RT), chemotherapy (CT) or both modalities (CT + RT). Over all sites a 50% increase in risk, relative to the West Midlands population, was found [observed (O) = 65; relative risk (RR) = 1.5; P less than 0.01]. Among patients treated by CT (with or without RT) a significant increase in acute and non-lymphocytic leukaemias was found (O = 6; RR = 30.0; P less than 0.001). The excess risk was of the order of 1 per 1000 patient-years and the cumulative risk was 1.2%. Among solid tumours increased risks, which might be attributable to RT, occurred in the lung (O = 15; RR = 1.6; P less than 0.05), breast (O = 9; RR = 2.2; P less than 0.05) and bone (O = 2; RR = 20.0; P less than 0.01). The excess of skin cancers (O = 13; RR = 2.9; P less than 0.01) occurred mainly within 10 years of treatment with CT. The follow-up period is still insufficient to determine the long-term effect on the incidence of solid tumours with long latent periods from multiple-agent CT which became more frequently used in the early 1970s. A sub-set of these data was analysed over all treatments and the results were contributed to an international study co-ordinated by the International Agency for Research on Cancer, Lyon.