The long-term cardiac effects of anterior-weighted thoracic mantle field radiotherapy were assessed in 25 patients treated for Hodgkin's disease. These patients underwent an evaluation that included a careful history and physical examination, ECG, M-mode echocardiogram, exercise ECG-gated radionuclide ventriculography, and cardiac catheterization. In these 25 patients evaluated 37-144 months (median, 96) after completion of thoracic mantle radiotherapy, eight had constrictive pericarditis; eight had occult constrictive pericarditis; three had an abnormal response to fluid challenge; three had suspected or proven occlusive coronary artery disease; and one each had a cardiomyopathy and diminished functional capacity on exercise testing. Only one patient appears to be normal after evaluation. The clinical spectrum of delayed-appearing radiation-induced cardiac disease in patients treated by anterior-weighted thoracic mantle fields and our suggestions for its treatment are discussed.