This study was designed to assess whether superior vena cava (SVC) Doppler flow velocities are associated with invasive measures of pulmonary arterial pressure. Eighty patients with unrepaired congenital heart disease who underwent cardiac catheterization were included (31 men, 49 women; mean age: 37.3 ± 14.7 y). Compared with the non-pulmonary hypertension group, the moderate and severe pulmonary hypertension groups had decreased SVC ventricular reserve flow velocity and a significantly increased ratio of atrial reverse flow to systolic flow (AR/S). AR/S correlated significantly with invasive pulmonary arterial systolic pressure (r = 0.426, p < 0.0001). A cutoff of 0.45 had a sensitivity and specificity of 74% and 80%, respectively, for prediction of pulmonary hypertension. Good correlation also existed between SVC AR/S and pulmonary arterial systolic pressure in cases without tricuspid regurgitation (r = 0.706, p = 0.034). These results indicate that SVC AR/S may be an alternative method for assessing pulmonary hypertension.