Osteonecrosis of the femoral and humeral heads is a serious complication of therapy for Hodgkin's disease and non-Hodgkin's lymphoma. Twenty-five patients were reassessed 5 years after being initially reported, in order to study the further progress and natural history of this complication. In addition, six recent patients who have also developed this condition are presented. With 5-year additional follow-up, no patient had developed symptoms of osteonecrosis in any bone other than those initially involved. Five patients developed severe complications thought to arise from their therapy suggesting that this group of patients were more sensitive to radiation injury than other patients treated with this modality. During the relatively short follow-up 5-year period, a surprising finding was the fact that 31% of the patients with Hodgkin's disease and 50% with non-Hodgkin's lymphoma had died. It is recommended that patients treated for lymphoma with steroid containing chemotherapy and radiotherapy be observed carefully for the occurrence of joint pain. Early diagnosis should lead to attempts to prevent total joint destruction.