Seven children or adolescents aged 8 to 20 years (average 13.5 years) underwent implantation of an apico-aortic conduit from 1980 to June 1989. Eleven previous operations under cardiopulmonary bypass had been performed. The indications were recurrence of muscular subaortic stenosis and/or congenital valvular stenosis in 3 cases, and stenotic, previously implanted aortic valve prosthesis of small calibre in 4 cases. The preoperative left ventricular-aortic systolic pressure gradient was between 70 and 130 mmHg. The first two patients had a bioprosthetic valvulation and the 5 succeeding patients a St Jude Medical mechanical prosthesis. The early and late mortality was nil. The average follow-up period is 5, 6 years at present (range 6 months to 9 years). One patient had to undergo repeat valve replacement after 5 years for degenerescence of the porcine bioprosthesis implanted in the conduit. No other complications related to the conduit or valve were observed. At the endpoint of the study all patients were asymptomatic without treatment. Control echocardiographic data showed normalisation of the indices of left ventricular function. Apico-aortic conduits would seem to be a safe and effective technique for the treatment of recurrent severe obstruction of the left ventricular outflow tract.