Primary balloon dilatation of supravalvar aortic stenosis was attempted in three patients: a 20 year old woman, a seven month old boy, and a 12 year old girl. Balloon catheters (Mansfield) with diameters of 25 mm, 8 mm, and 15 mm were used in the three patients respectively. The systolic pressure gradient across the aortic narrowing decreased considerably and the diameter of the constricted area increased significantly. Balloon dilatation was feasible and provided good immediate results and sustained relief of supravalvar aortic stenosis in these three patients. However, a larger study is needed to establish the place of this procedure in treatment.