BACKGROUND: The oxidative modification of lipids and the endothelial expression of adhesion molecules are key events in the pathogenesis of atherosclerosis. The appropriate antioxidants that protected and slowed the progression of the disease were reported. We measured the antioxidant enzyme activities and the levels of soluble cellular adhesion molecules in order to evaluate whether antioxidant vitamin supplementation affected the oxidative changes and the expression of cellular adhesion molecules. METHODS: Seventy-seven patients participated in a randomized, double blind, placebo-controlled trial. The test group (38 patients) was given antioxidant vitamin doses including a daily dose of vitamin C 500 mg, beta-carotene 15 mg, vitamin E 400 IUs, and selenium 50 microgram, The control group (44 patients) received placeboes for three months. We measured the vitamin serum levels, intercellular adhesion molecules-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin and activities of erythrocyte enzymes such as superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPX) before and at 3 months after supplementation. RESULTS: After supplementation, the serum vitamin levels increased significantly (P<0.05) and the activity of the erythrocyte SOD significantly increased by 0.85 unit/mg hemoglobin (P<0.05) in the test group. Soluble ICAM-1, VCAM-1 and E-selectin levels did not change significantly in the test group after supplementation. CONCLUSIONS: These results suggest that the antioxidant vitamin supplementation may affect erythrocyte SOD activity, but not soluble cellular adhesion molecule levels.