In this paper, we report the results of experimental and clinical studies of the pulmonary vein with Doppler echocardiography in 188 cardiac patients and normal controls. 1. The diameter of the right superior pulmonary vein (RSPV): The diameter of the RSPV was 9.8 +/- 0.2 mm in normals and significantly dilated in the groups with passive or active pulmonary hypervolemia and decreased in the group with pulmonary hypovolemia (p less than 0.001). 2. Blood flow velocity of RSPV: The blood flow velocity of the RSPV measured in normal controls by Doppler echocardiography was 35.7 +/- 3.2 cm/s and significantly decreased in the groups with passive pulmonary hypervolemia and pulmonary hypovolemia (19.6 +/- 7.8 cm/s and 25.2 +/- 9.4 cm/s, respectively) and increased in the group with active pulmonary hypervolemia (49.6 +/- 19 cm/s, p less than 0.001). 3. Blood flow of RSPV: Blood flow of the RSPV was 2.3 +/- 1.5 L/m in normals, 3.4 +/- 2.4 L/m in the group with passive pulmonary hypervolemia, 6.2 +/- 2.9 L/m in the group with active pulmonary hypervolemia and 0.7 +/- 0.5 L/m in the group with pulmonary hypovolemia. Blood flow in the active pulmonary hypervolemic group was higher than that in the passive pulmonary hypervolemic group and the hypovolemic group. There was a high correlation between the pulmonary blood flow measured by Fick's method (Qp) and RSPV flow (RSPVF) measured by echocardiography (Qp = 1.96, RSPVF 0.92, r = 0.81, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)