The pattern of circulating monocyte subtypes and the concentration of the soluble intercellular adhesion molecule-1 (ICAM-1) were compared in middle-aged female moderate smokers and lifetime non-smokers. Total leukocyte and monocyte counts were higher in smokers. The pattern of circulating monocytes of smokers was changed toward lower absolute counts of activated (CD16+/CD64+) monocytes and (CD16+/CD14+) monocyte-macrophages and higher counts of nonactivated monocytes. The serum concentration of soluble ICAM-1 was significantly higher in smokers than in non-smokers. It is supposed that even moderate cigarette smoking leads to an activation of the circulating monocytes and their increased adhesion to the endothelium.