Monocyte adhesion to endothelium appearing determinant in atherosclerosis, the possibility that circulating monocytes have an increase of their adherence on endothelial cells were investigated in patients with atherosclerosis. The adherence of circulating monocytes on endothelial cell monolayers was determined in 26 patients with atherosclerosis (age 59 +/- 4), and 25 healthy individuals (age 55 +/- 4). No difference of monocyte adherence was observed between the two groups (18.8 +/- 13.8% vs 19.2 +/- 13.4%), or following atherosclerosis severity. However, monocyte adherence appeared positively correlated to smoking habits (r = 0.34, P < 0.02) and fibrinogen level (r = 0.31, P < 0.03), and negatively to the degree of plasmatic LDL oxidation (r = -0.28, P < 0.05). These results suggest that the adherence of monocytes to endothelial cells is not increased in atherosclerosis, but enhanced by risk factors. A weak plasmatic LDL oxidation could inhibit monocyte adhesion.