The objective of this study was to determine if the pressure drop across various types of aortic-pulmonary shunts could be accurately estimated by Doppler echocardiography, and if systolic pulmonary pressure could be estimated by referencing the pressure drop across the aortic-pulmonary shunt to systolic systemic arterial pressure measured by cuff sphygmomanometry. This was done in 22 patients and Doppler results were compared with pulmonary artery pressure measured directly by strain gauge manometry. Adequate Doppler waveforms were obtained in 21 of 22 patients; 3 had a Waterston shunt, 10 had a Blalock-Taussig shunt, 1 had a left pulmonary artery-aortic anastomosis, 6 had a patent ductus arteriosus and 1 had an aortic-pulmonary window. Systolic pulmonary artery pressure estimated by Doppler echocardiography ranged from 12 to 90 mm Hg (mean 41.3 +/- 21.4 [SD] ), and measured by strain gauge manometry ranged from 20 to 90 mm Hg (mean 44.7 +/- 20.7) (p = NS, r = 0.94, SEE = 7.4 mm Hg; slope = 0.90, y intercept = 7.4 mm Hg). Systolic pulmonary artery to aortic pressure ratios predicted by Doppler recording ranged from 0.1 to 1.0 (mean 0.4 +/- 0.2 [SD] ); when calculated from direct measurement it ranged from 0.2 to 1.0 (mean 0.4 +/- 0.2) (p = NS, r = 0.92; SEE = 0.08, slope = 0.80, y intercept = 0.09). This study demonstrates that Doppler echocardiography provides an estimation of pressure drop across aortic-pulmonary shunts, and that the data can be used to estimate systolic pulmonary artery pressure by subtracting the estimated pressure drop from the systolic systemic arterial pressure.