The incidence of relapses and second malignant neoplasms was investigated in a group of 148 patients with bad-risk stage II, or stage III and IV Hodgkin's disease treated with a MOPP-modified protocol between 1973 and 1979. Sixty-eight patients received chemotherapy alone, 80 a combined modality treatment including radiotherapy. One hundred and twelve patients achieved complete remission with induction therapy. Thirty-six patients relapsed 3-120 months (median 27 months) after the induction program with a 10-year cumulative risk of relapse of 33.6%. Seven out of 112 complete responders developed a second malignancy 65-145 months from the start of therapy; one more neoplasm has been recorded in a patient with active Hodgkin's disease. Survival after diagnosis of second malignant neoplasm did not exceed 12 months. The cumulative risk of developing a second malignancy was 6.2% at 10 years. The free-from-failure survival was 49.2% at 10 years, being 64.7% for patients achieving complete remission and 92.4% for long-term complete responders. Although an increased number of second malignant neoplasms may occur in patients treated for Hodgkin's disease, the high risk of early relapse, together with the limited effectiveness of salvage therapy, suggests that intensive induction programs should be carried out in patients with advanced or poor-prognosis Hodgkin's disease in order to achieve long-lasting complete remission.