In order to clarify whether hemodialysis treatment accelerates atherosclerosis, forty-two patients undergoing chronic hemodialysis were investigated. Because it is non-invasive and repeatable, aortic calcification on chest-XP was used as an index of atherosclerosis. No patients had evidence of calcified atherosclerosis at the start of hemodialysis therapy. The patients were divided into three groups according to vascular changes. Group 1 (20 patients) showed no calcification during the observation period. Group 2 (11 patients) had mild or moderate aortic calcification (thin linear aortic calcification). In group 3 (11 patients), massive and severe calcification was accelerated by hemodialysis. 18 parameters which might be considered to promote atherosclerosis were evaluated in each group. The age in group 3 was 53.8 +/- 10.4 (mean +/- standard deviation) years, which was older than the 42.1 +/- 12.6 year age in group 1 (p less than 0.025). Duration of dialysis in group 3 was 121.9 +/- 30.5 months, which was significantly longer than the 82.0 +/- 31.0 months in group 2 (p less than 0.01) and the 77.3 +/- 55.3 months in group 1 (p less than 0.025). Serum HDL-cholesterol levels in groups 2 (23.0 +/- 4.5 mg/dl) and 3 (20.9 +/- 6.6 mg/dl) were significantly lower than the 28.6 +/- 8.3 mg/dl in group 1, (p less than 0.025 and p less than 0.05, respectively). Serum parathormone-C level in group 3 was 14.7 +/- 8.6 ng/ml, which was significantly higher than the 6.1 +/- 6.0 ng/ml level in group 1 (p less than 0.01) and the 5.0 +/- 7.8 ng/ml level in group 2 (p less than 0.025). In discriminant analysis, age, duration of dialysis, hematocrit, serum HDL-cholesterol, parathormone-C, and alkaline phosphatase level were the independent factors used to distinguish the three groups. These findings suggest that 1) aging is a basal factor in the promotion of atherosclerosis, 2) hypo-HDL cholesterolemia is a major factor in the early phase of atherosclerosis, 3) hyperparathyroidism could have an important role in the late phase of atherosclerosis, 4) dialysis itself might promote atherosclerosis directly, and 5) blood pressure level is not major factor for atherosclerosis over a long observation period, at least in our study.