Experience with stepwise balloon dilatation of congenital aortic valve stenosis using the new Inoue balloon catheter in 16 patients (aged 12 +/- 4.6 years; group II) is presented. Results are compared with those obtained in 15 patients (10 +/- 6 years; group I) in whom standard balloon catheters were used. The procedure resulted in a similar transvalvar gradient reduction in both groups (83 +/- 25 to 34 +/- 14 mmHg in group I versus 84 +/- 21 to 28 +/- 10 mmHg in group II). Significant aortic incompetence occurred in three patients from group I and in four from group II. There was no difference in the average increase in AR grade between the groups. At follow-up (group I, 24 +/- 13 months; group II, 7 +/- 3 months) there was no significant change in transaortic gradient or aortic incompetence. Balloon aortic valvuloplasty for congenital aortic stenosis carries a risk of aortic incompetence. Stepwise dilatation of the stenosis does not prevent this complication. The Inoue balloon catheter offers technical advantages.