Between January and December, 1987, a programme of heart transplantation in paediatrics was designed and carried out in 9 children by the medical and surgical teams of the Necker/Enfants Malades-Laënnec hospitals group, Paris. Six of the patients were infants of less than 2 years (4 were under one year), and the oldest child was 10 years old. All patients seemed to be condemned to an early death either because their congenital heart disease was beyond the resources of conventional surgery (6 cases) or because their dilated cardiomyopathy was refractory to all medical treatments. Three children died at the end of the operation or a few days afterwards, due to poor quality graft (1 case), fulminating bacterial superinfection (1 case) or intractable pulmonary hypertension (1 case). The remaining 6 children are now living as normally as possible in their respective families. The long-term immunosuppressive treatment consists of cyclosporine and azathrioprine; corticosteroids are only used at the very beginning of treatment or in case of graft rejection. Only two episodes of rejection, confirmed by endomyocardial biopsy, were observed in the same patient during the first postoperative month. Biopsy was never performed systematically in order to spare the patient's vein, and the diagnosis of rejection was suspected on clinical grounds.(ABSTRACT TRUNCATED AT 250 WORDS)