Twenty-six infants aged 10 days-11 months (mean 3.5 +/- 2.4 months), with critical aortic stenosis underwent aortic valve balloon dilatation in last six years. In 19 (73%) infants, aortic valve balloon dilatation had to be performed as an emergency procedure. The systolic gradients decreased from 71.7 +/- 11.8 mm Hg to 21.0 +/- 8.1 mm Hg. There was no procedural death. Severe aortic regurgitation developed in two (7.7%) which was medically managed. Four (15.4%) infants had femoral artery thrombosis following aortic valve balloon dilatation and all responded to intravenous streptokinase. Congestive heart failure resolved in all (100%). Two infants developed endocarditis during follow-up after aortic valve balloon dilation and one of them died, another patient died of severe pulmonary artery hypertension. In the surviving 24 infants, left ventricular function improved markedly. On follow-up of 18 +/- 5 months, restenosis developed in two (7.7%) patients. We conclude that aortic valve balloon dilatation is safe and effective treatment for infants with critical aortic stenosis and severe left ventricular dysfunction.