During the 20 years between 1973 and 1992, 27 patients were identified in whom cardiac tissue was available (15 surgical, 10 autopsy, and 2 both) that exhibited radiation-related injury. Specimens were assessed for damage to the pericardium, valves, myocardium, and coronary arteries. Patients ranged in age from 22 to 76 years (mean, 49 years), and 19 were men. Among 20 cases with available pericardium, 14 (70%) had radiation-related disease including six with an effusion, three with constriction, two with both, and three with neither. In 17 cases with available valves, 12 (71%) showed radiation injury involving 25 valves (nine mitral, eight aortic, five tricuspid, and three pulmonary), although clinically significant dysfunction was diagnosed in only eight. For the 16 patients from whom myocardium was available, 10 (63%) exhibited radiation-related fibrosis, which was moderate or severe in only the seven who received more than 3,000 rad (cGy). Among the 13 cases with available coronary arteries, only two had unequivocal radiation-induced obstructions (26- and 44-year-old men with Hodgkin's disease). In conclusion, radiation injury to the heart includes not only constrictive pericarditis and myocardial fibrosis, but also appreciable valvular and coronary artery lesions. As patients with malignancies survive longer, the surgical relief of radiation-induced heart disease may become more prevalent.