Twenty-eight patients younger than age 40 years, treated for Hodgkin's disease with mediastinal irradiation, were examined no less than 5 years after the irradiation in order to evaluate the frequency of cardiac abnormalities. Twelve patients (43%) had had some pericardial event after radiation: a diagnosed pericarditis, remarkably increased heart volume, or a conspicuous change of cardiac silhouette, suggesting pericardial fluid. On evaluation, 50% of the patients complained of symptoms, and 13 patients had to stop the exercise test on a low level because of chest pain, dyspnea, or general fatigue. In 13 patients some of the following abnormalities in the electrocardiogram (ECG) was found: right bundle branch block (four), first-degree atrioventricular block (four), abnormal P terminal force (five), or a low voltage (two). In ten patients (38%) an increase of the pericardial fluid was seen in the echocardiogram, and in nine patients the right ventricle wall thickness had increased. In two patients a severe coronary artery disease was found. One died suddenly after an acute myocardial infarction (AMI), and the other had a large anterior AMI. Two patients with chronic pericardial fluid underwent partial pericardectomy. Two cases of mild pulmonary valve stenosis, one pulmonary subvalvular stenosis and two aortic valve deformities were discovered. Eight patients went through cardiac catheterization, and in all but one case the pressures were slightly elevated suggesting diminished diastolic compliance. In summary, 19 of 28 patients had some abnormal cardiac findings, but only three of them were serious ones.