Noninvasive assessment of pulmonary vascular resistance has not been well defined. Cardiac catheterization findings in 33 patients with congenital heart disease (mean age 1.4 years) were compared with Doppler echocardiographic parameters. The right ventricular pre-ejection period (RVPEP), ejection time (RVET), and the ration RVPEP/RVET correlated better with pulmonary vascular resistance than with pulmonary artery pressure. A highly significant correlation with a small standard error of estimate (SEE) was demonstrated between pulmonary vascular resistance and a newly derived parameter RVPEP/velocity time integral (VTI) [r = 0.87, p < 0.0001, SEE = 2]. An RVPEP/VTI value of < 0.4 seconds/meter (M) was able to select patients with pulmonary vascular resistance < 3 Wood Unit.M2, even in the presence of pulmonary artery hypertension caused by increased pulmonary blood flow, with 97% accuracy (100% sensitivity, and 92% specificity). An RVPEP/VTI value of 0.4 to 0.6 seconds/M identified patients with pulmonary vascular resistance between 3 to 7.5 Wood Unit.M2 with 91% accuracy, and a value of > or = 0.6 seconds/ M selected patients with total pulmonary vascular resistance > or = 7.5 Wood Unit.M2 with 94% accuracy.