Children with valvar pulmonary stenosis have right ventricular diastolic filling abnormalities that may be due to either right ventricular hypertrophy or right ventricular outflow obstruction. In order to investigate the reason for this abnormality, 23 consecutive cases with pulmonary stenosis (mean age 7.94 +/- 3.33 years) undergoing transluminal pulmonary balloon valvuloplasty without significant tricuspid or pulmonary valvar regurgitation were studied prospectively. Right ventricular diastolic filling indices and pulmonary valvar systolic gradients were measured in these children one day before and after pulmonary balloon valvuloplasty and were re-examined six months later. Right ventricular diastolic indices based on rapid early diastolic filling peak velocity (peak E), peak velocity during atrial contraction (peak A), and ratio of E/A were determined by pulsed Doppler echocardiography. In conclusion, right ventricular diastolic filling indices in patients with pulmonary stenosis did not improve after pulmonary balloon valvuloplasty in the first day but when re-examined by the sixth month there was a significant improvement. These data suggest that diastolic filling abnormalities are more likely a result of right ventricular hypertrophy than of right ventricular outflow obstruction.