Forty-eight children with suspected isolated pulmonary valvar stenosis were evaluated clinically and echocardiographically between January 1987 and December 1988. Fourteen patients with significant transpulmonary peak systolic pressure gradient greater than 30 mmHg on continuous-wave Doppler interrogation were subjected to right heart catheterisation. Percutaneous transluminal balloon valvuloplasty was performed in 11 of these patients with peak systolic pressure gradient than 40 mmHg across the pulmonary valve at cardiac catheterisation. Satisfactory reduction of systolic right ventricular pressure (110 +/- 43 to 46 +/- 17 mmHg, p less than 0.001) and peak systolic pressure gradient across pulmonary valve (92 +/- 44 to 27 +/- 16 mmHg, p less than 0.001), were achieved in all cases. The reduction of peak systolic pressure gradient (64 +/- 37 mmHg, range = 29-158 mmHg), was positively correlated with the initial right ventricular systolic pressure (r = 0.92, p less than 0.0002). There was no significant complication in this series and all patients were discharged the day after the procedure. Percutaneous transluminal balloon valvuloplasty is effective and safe. It should be the treatment of choice for significant valvar pulmonary stenosis in children.