To evaluate the restenosis rate after successful balloon aortic valvuloplasty, clinical evaluation and repeat catheterization were performed in 96 patients who had undergone balloon dilatation 7 +/- 5 months earlier. Restenosis, defined as a loss of greater than 50% of the benefit in aortic valve area obtained after balloon valvuloplasty, was observed in 48% of the patients. Actuarial analysis showed that the restenosis rate was time dependent and was 80% at 15 months. However, functional improvement was observed in most of the patients with or without restenosis. The restenosis rate was not correlated with the degree of enlargement of the aortic orifice produced by the valvuloplasty procedure. Because of the high incidence of restenosis, balloon aortic valvuloplasty should be limited to patients who have a contraindication to surgery or are at high risk for surgery, or as a bridge to surgery.