Data from 204 children and infants who underwent aortic balloon valvuloplasty between 1982 and 1986, reported to the Valvuloplasty and Angioplasty of Congenital Anomalies Registry, were reviewed. Valvuloplasty was successful in 192 of 204 children, reducing the peak systolic left ventricular ejection gradient from 77 +/- 2 to 30 +/- 1 mm Hg, p less than 0.001. The same degree of aortic stenosis gradients reduction was noted in both the 38 children under 1 year of age and in the 166 children over 1 year of age. Significant complications included death, aortic regurgitation and femoral artery thrombosis or damage. The incidence of these complications correlated with the age of the child, the ratio of valvuloplasty balloon size/anulus size, or both. The data suggest that percutaneous balloon valvuloplasty provides effective acute relief of valvar aortic stenosis in both infants and children. However, long-term follow-up data are necessary before balloon valvuloplasty can be established as a treatment of choice for congenital valvar aortic stenosis.