Calcification in the pulmonary artery (PA) occurs in rare cases. There have been no studies of calcification in the PA at the site of its contact with a left coronary artery bypass graft (CABG). In the present study, X-ray computed tomography (CT) was employed for examination of such calcification. The subjects were 53 patients (49 male and 4 female, mean age of 56.7 years) who underwent 74 left CABGs (69 saphenous veins and five internal thoracic arteries). Following surgery, non-contrasted CT was performed from the lower level of the aortic arch to the lower boundary of the left ventricle at 5-mm horizontal intervals, and contrasted CT was performed at the level of the PA; this procedure was repeated at approximately six-month intervals after the operation. In addition, aortography and selective graft angiography were carried out at 7.6 months postoperatively. The inner diameter of the grafts and the levels of serum cholesterol were also examined. Calcification in the PA was detected in 24 cases (all of them saphenous vein grafts), but graft angiography found no stenosis in those sites. Calcification size varied from 1 mm to 14 mm, with 10 of the cases at or exceeding 10 mm and showing high density. Only three of the cases enlarged with time. Calcification appeared at 2.9 to 54.3 months postoperatively and the mean time of onset was 10.0 +/- 15.7 months. The mean age of the patients with PA calcification was 58.7 +/- 5.9 years while that of the patients without calcification was 57.3 +/- 10.0 years. Graft diameter was 5.9 +/- 1.9 mm in the former group and 5.6 +/- 1.7 mm in the latter. Serum cholesterol level was 235 +/- 32 mg/dl in the former group and 243 +/- 42 mg/dl in the latter. There were three cases of occlusion in the calcification group, and four in the other. There were no significant intergroup differences in these four parameters. The incidence of CT-detected calcification in the PA was found to be high at its point of contact with saphenous vein grafts.