Percutaneous transluminal balloon valvuloplasty has been used in children since 1983 to treat tight aortic valve stenosis. Although more than 100 cases have been published, its indications compared with those of surgical valvulotomy have not yet been clearly defined. Twelve patients with tight aortic valve stenosis underwent transluminal balloon valvuloplasty: 3 were infants whose ages ranged from 1 month and 24 days to 3 months and 23 days (mean 80 +/- 13.7 days), and 9 were children aged from 4 to 17 years (mean 10.44 +/- 4.61 years). Aortic regurgitation grade I (5) or grade III (1) was present in 6 cases. An 8-year old child had previously undergone surgical aortic valvulotomy simultaneously with repair of aortic coarctation. Other associated malformations were congenital grade III mitral regurgitation in 1 case and Turner's syndrome in 1 case. Dilatation was performed with one or two successive balloons in 11 patients and with two balloons concomitantly in 1 patient. The diameter of the balloon (or the sum of those of the two balloons) was 77 to 112 percent of the diameter of the aortic annulus, but in one case this figure rose to 119 percent after failure of dilatation with a smaller balloon. One infant died at the end of the dilatation, due to perforation of the left ventricle. Another infant developed inferior myocardial infarction which followed a favourable course and left minimal sequelae.(ABSTRACT TRUNCATED AT 250 WORDS)