Occult or overt but delayed cardiac disease after thoracic radiotherapy for Hodgkin's disease may be common. Detailed cardiac evaluation was performed in 108 patients, mean age 46 +/- 6.2 years, with Hodgkin's disease at 175 +/- 43 months after irradiation. The study protocol included clinical examination, graded treadmill exercise test and echocardiography. Some patients with angina pectoris, previous myocardial infarction and an abnormal ECG were studied by thallium-201 scintigraphy, cardiac catheterization and coronary angiography. Cardiac disease was found in 12 patients (11%). Three patients had angina pectoris, one patient had myocardial infarction, two complained of dyspnea on effort and two had congestive heart failure. At catheterization, constrictive pericarditis was diagnosed in four patients; in two additional patients an occult constrictive pericarditis was found. One patient had both mitral and tricuspidal regurgitation and one had mitral regurgitation alone. Eight patients (7.4%) had severe coronary artery disease; four of these had associated constrictive pericarditis. Four patients had a pericardiectomy and another four had undergone coronary artery by-pass graft. Two patients died after operation from persistent pericardial constriction. It is concluded that the incidence of delayed cardiac disease after radiotherapy is relatively high; chronic pericardial disorders and coronary artery disease are the most frequent manifestations of this disease. Standard surgical treatment may be beneficial because of the relative youth of these patients.