Between March, 1985 and April, 1987, 25 orthotopic heart transplantations were performed in 20 men and 5 women aged from 17 to 58 years (mean 42 years) on account of cardiomyopathy (n = 15), ischaemic heart disease (n = 6) or miscellaneous lesions (n = 4). The immunosuppressive treatment consisted of antilymphocyte serum and corticosteroids during 10 days; cyclosporine was introduced on the 7th day and continued thereafter in association with low-dose corticosteroid therapy. Endomyocardial biopsies were performed. Acute rejection, responsible for 2 deaths (one on the 10th day, the other in the 10th week), usually occurred within the first 3 months. Infections were frequent and often serious, resulting in one death in the 7th week. One out of patients had to be treated for arterial hypertension, and 3 patients presented with renal impairment (blood creatinine over 200 mumoles/l). The actuarial survival rate at 2 years is 84 p. 100. More than one-half of the patients have resumed social and occupational activities.