Since November 1985, forty-four heart transplants have been accomplished in 43 infants and children younger than 12 years of age. Indications for transplantation included structural heart disease (31 patients), idiopathic or viral cardiomyopathy (10 patients), and combined structural and myopathic disease (2 patients). Postoperative recipient surveillance was achieved noninvasively during the first year of life; endomyocardial biopsy was employed in children. Maintenance immunosuppression included cyclosporine and azathioprine therapy during the first year after transplantation in young infants, graduating to cyclosporine therapy alone beyond the first year. Azathioprine therapy was continued indefinitely in children. There have been 5 perioperative deaths and 1 late death in this series of recipients. Overall survival was 86%. Growth, development, and psychosocial adjustments generally have been excellent. Donor heart growth has been normal. Coronary artery disease has not yet been observed. Our findings indicate that heart transplantation seems to be effective therapy for selected incurable pediatric cardiac diseases.