Background Circulating leukocytes are recruited at atherosclerotic sites through a family of adhesion molecules, Circulating forms of adhesion molecules in peripheral blood can be quantified now. Objective To evaluate the relationship between circulating adhesion molecules and severity of coronary atherosclerosis. Methods Subjects included 81 patients undergoing diagnostic coronary angiography, 12 of whom had normal coronary arteries (control group). The remaining 69 patients with demonstrable coronary atherosclerosis were divided into two groups by use of Gensini scores, namely mild atherosclerosis (n = 36, Gensini score 1-20) and severe atherosclerosis (n = 33, Gensini score >20). Serum levels of circulating intercellular adhesion molecule-1 (ICAM-1), vascular cellular adhesion molecule-1 (VCAM-1), and E-selectin of groups measured before angiography were compared. Results Circulating levels of ICAM-1 in members of mild and severe atherosclerosis groups were significantly higher than those in members of the control group, whereas there was no significant difference among circulating levels of VCAM-1 in members of the three groups. Circulating levels of E-selectin in members of the mild atherosclerosis group were significantly higher than those in members of the severe atherosclerosis and control groups. Conclusions These findings suggest that E-selectin is related to the early stage, and ICAM-1 is related to the advanced stage, of coronary atherosclerosis. With progression of atherosclerosis, one-step adhesion by ICAM-1 could become more important than multistep adhesion involving E-selectin, ICAM-1, and VCAM-1. These molecules may serve as markers for severity of coronary atherosclerosis, Coronary Artery Dis 11:77-81 (C) 2000 Lippincott Williams & Wilkins.