To determine whether pulmonary arterial hypertension (PAH) and pulmonary venous hypertension (PVH) can be differentiated noninvasively, we reviewed data on 44 patients with pulmonary artery systolic pressure greater than or equal to 40 mm Hg by echocardiography and cardiac catheterization performed within 7 days of each other. Based on left ventricular end-diastolic pressure or pulmonary capillary wedge pressure, 20 patients were classified as having PVH and 24 as having PAH. Early (E) and late (A) diastolic mitral inflow velocities, deceleration time, early diastolic mitral annular velocity (E'), and E/A and E/E' ratios were remeasured in the two groups. Compared with patients with PAH, those with PVH had significantly higher E (107.8 +/- 27.3 vs 65.0 +/- 24.0 cm/s, P < .001), E/A (2.4 +/- 1.0 vs 0.9 +/- 0.4, P < .001), and E/E' (14.3 +/- 4.3 vs 5.1 +/- 1.9, P < .001), and significantly lower A (55.5 +/- 33.5 vs 74.1 +/- 20.8 cm/s, P < .001), E' (8.0 +/- 2.5 vs 13.1 +/- 3.6 cm/s, P = .001), and deceleration time (148.5 +/- 49.0 vs 192.3 +/- 41.9 milliseconds, P = .003). The area under receiver operating characteristic curve was 97% for E/E' and 91% for E/A. Optimal cutoff for diagnosing PVH was 9.2 for E/E' (sensitivity 95%, specificity 96%) and 1.7 for E/A (sensitivity 75%, specificity 91%). PAH and PVH may be differentiated by readily obtainable conventional and tissue Doppler parameters.