The patterns of early and late relapses (those occurring later than 3 years after diagnosis) in 432 patients achieving complete remission after treatment for stage I and II Hodgkin's disease at the Royal Marsden Hospital between 1964 and 1983 were studied to identify factors predicting for late relapse. The incidence of early relapse has fallen progressively in recent treatment eras as staging procedures and management have improved but in contrast there has been no decrease in the risk of late relapse. The incidence of late relapse was greater in patients treated with radiotherapy rather than combined modality therapy (P less than 0.05). However, patients who were clinically staged and treated with combined modality therapy retained as high a risk of relapse between 3 and 6 years as in years 2 and 3. The risk of late relapse was also greater in patients with stage II disease and in those without B symptoms at presentation. Patients falling into the higher risk categories for late relapse require continued close follow-up beyond 3 years to monitor for possible relapse.