We evaluated the clinical significance of the configuration of right ventricular pressure curves after balloon valvoplasty in 35 patients with pulmonary valvar stenosis. Right ventricular pressures were measured with a fluidfilled catheter. We divided the subjects into two groups according to the pressure curves seen after balloon valvoplasty. In eight patients, two peaks were found in the curves, with the higher peak occurring at late systole. The remaining 27 patients had a single peak observed during early to mid systole. In all patients in the group with a single peak, the ratio of ventricular pressures decreased by more than half, and no residual narrowing was seen in right ventricular outflow tract, the diameter after valvoplasty increasing by more than half over the diameter before the procedure. In contrast, in five of eight patients in the group with double peaks in the pressure curves, the ratio between ventricular pressures remained higher than 0.5, and the diameter of the right ventricular infundibulum was reduced to less than half the diameter prior to balloon valvoplasty. In three of these patients with double peaked pressure contours, to whom propranolol was administered intravenously, the pressure configuration changed to one with a single peak and the ventricular pressure ratio fell to below 0.5. The degree of obstruction of the right ventricular infundibulum also decreased. These data suggest that a high right ventricular pressure and two peaks in the pressure curve with the higher peak at late systole after balloon valvoplasty indicate, first, the presence of a significant narrowing in the right ventricular outflow tract and, second, effective balloon valvoplasty.