The diameters of the pulmonary veins at their atrial junction were measured from cineangiocardiographic films in 27 children (mean height 128.5 cm) without heart disease. Right upper pulmonary veins and right lower pulmonary veins were measured in all 27 films. The left upper pulmonary veins could be measured in 23 children (mean height 127.0 cm), and the left lower pulmonary veins only in 15 (mean height 135.0 cm) because their atrial junctions were obscured by other structures. Measurements were obtained in frontal projection of levophase of pulmonary trunk angiograms. Calipers and a micrometer were used and the values were expressed to the nearest 0.5 mm. The measured size of the intracardiac catheter was used for calibration. The diameter (in mm) for right upper pulmonary veins was 0.08 x height (in cm) + 1.4 (r = 0.96); for right lower pulmonary veins, 0.07 x height + 2.1 (r = 0.94); for left upper pulmonary veins, 0.06 x height + 3.1 (r = 0.87); and for left lower pulmonary veins it was the same as for left upper, but with r of 0.94.