PURPOSE: To retrospectively establish normal values for pulmonary vein diameter, cross-sectional area, and shape depicted at computed tomography (CT). MATERIALS AND METHODS: Institutional review board waived patient consent requirement and approved the study. Thin-section contrast material-enhanced spiral chest CT scans in 104 patients, 68 women and 36 men (age range, 19-86 years; mean, 49 years) referred to exclude pulmonary embolism, were retrospectively reviewed. Short-axis diameter and cross-sectional area of the four major pulmonary veins (right inferior and superior, left inferior and superior) were measured at a workstation by using oblique reconstructions. Each vein was measured at six locations, 5 mm apart, starting at atrial ostium. Each measurement was performed three times by an experienced thoracic radiologist, and the mean value was recorded. Roundness was estimated by comparing the ratio of the calculated cross-sectional area to that measured. Mixed effects model was used to compare men and women relative to the distribution of diameters and surface areas and to compare roundness of the right and left veins. RESULTS: Mean pulmonary vein diameters at the ostia were variable: right superior, 11.4-12.4 mm; left superior, 9.6-10.5 mm; right inferior, 12.3-13.1 mm; and left inferior, 9.0-9.9 mm. Diameter and cross-sectional area of the left superior pulmonary vein were significantly larger in men than in women (P < .005). As expected, the caliber of three of the four veins gradually increased as they approached the left atrium. Caliber of the left inferior pulmonary vein decreased as it entered the left atrium. None of the veins were round; all were ovoid. Left-sided veins and venous ostia were less round than right-sided veins (P < .001). CONCLUSION: Pulmonary vein diameter, cross-sectional area, and shape vary. Particular care must be taken when the left inferior pulmonary vein is evaluated for stenosis, as it normally narrows as it enters the left atrium.