Balloon valvuloplasty (BV) in neonates with critical pulmonary valve stenosis (CPVS) is limited by technical considerations, mainly the difficulty of traversing the stenotic valve, To simplify the procedure we used a 46 Cobra Type I catheter to cross the pulmonary valve (PV) without the aid of a guidewire, and performed single-stage BV, using low-profile balloons, in 12 neonates with CPVS, Procedure and total fluoroscopy times were 69+/-33 min (42-125 min) and 34+/-19 min (20-58 min), respectively, Following BV, right ventricular systolic pressure (RVSP) decreased from 102+/-17 mm Hg to 56+/-15 mm Hg (p <0.001); and the ratio of RVSP to aortic systolic pressure decreased from 1.39+/-0.22 to 0.73+/-0.21 (p <0.001). No significant complications were observed, BV failed in two patients, who subsequently had surgery, At follow-up (a mean of 19 months), Doppler gradient was 19+/-12 mm Hg (0-50 mm Hg). BV was repeated in one patient. We conclude that in neonates with CPVS, the use of the 4F Cobra type I catheter facilitates crossing of the PV and allows performance of BV in a single stage; this enhances safety and time-efficiency, and shortens exposure to radiation. (C) 1997 Wiley-Liss, Inc.