Pulmonary vein stenosis was diagnosed by transesophageal echocardiography in five patients who underwent the study for different clinical indications. Stenosis was encountered in the right upper pulmonary vein in two patients, the right lower pulmonary vein in two patients, and at the confluence of the left pulmonary veins in one patient. In only one patient was the diagnosis suspected on transthoracic echocardiography. Contralateral normal veins from the same patient served as the control. Vessel diameter and peak flow velocity were measured and compared. The diameter of the stenosed veins ranged from 0.3 to 0.8 cm (mean 0.4±0.09 cm [SEM]), whereas for normal veins the diameter was 0.9 to 1.2 cm (mean 1.0±0.05 cm [SEM]; p<0.001). Peak flow velocity in the stenosed veins ranged from 1.1 to 1.6 m/sec (mean 1.4±0.1 m/sec [SEM]), whereas in normal veins peak flow velocity ranged from 0.4 to 0.7 m/sec (mean 0.6±0.04 m/sec [SEM]; p<0.001). There was a strong negative correlation between vessel diameter and peak flow velocity (R=0.89; p<0.001). Peak flow velocity of 0.8 m/sec appears to provide the best separation between normal and stenosed pulmonary veins. We conclude that pulmonary vein stenosis is associated with increased flow velocity and turbulence and deformity of the flow signal. Transesophageal echocardiography is a powerful tool in the study of pulmonary vein stenosis.