A study of the relationship between bulk disease and sites of relapse has been undertaken in 95 patients treated by radiotherapy for early stage Hodgkin's disease. All patients were investigated and treated according to protocols of the British National Lymphoma Investigation. In a group of 80 pathologically staged patients the pattern of relapse in 39 patients confirms an association between recurrence and sites of bulk involvement in the mediastinum, neck and axilla. Bulk disease predisposes to recurrence by virtue of local failure inside the treatment volume as well as marginal recurrence. A small number of patients relapsed initially in sites that were irradiated prophylactically.