A new technique of percutaneous gradational balloon pulmonary valvuloplasty was used successfully in 17 infants less than 1 year of age, including four neonates, with critical congenital pulmonary valve stenosis, who would otherwise have required surgical intervention. This technique uses a sequential series of balloon catheters of gradually increasing size as a means of eventually crossing the very small valve orifice with a balloon catheter of adequate size to achieve successful pulmonary valvuloplasty. The initial dilatations were achieved with balloon catheters 2, 3, or 4 mm in diameter. Immediately after successful balloon valvuloplasty, the mean pulmonary systolic pressure gradient was reduced from 105 +/- 11 to 20 +/- 5 mm Hg. Percutaneous balloon pulmonary valvuloplasty can be performed safely with good results despite critical congenital pulmonary valve obstruction in severely ill infants.