Background Monocyte chemoattractant protein-1 (MCP-1) is involved in the recruitment of monocytes into the arterial vessel wall as one of the major events leading to atherosclerotic vascular diseases, such as coronary artery disease (CAD). Methods and Results The study group comprised 263 volunteers aged between 18 and 85 years who were admitted to hospital or clinic for scheduled invasive and non-invasive diagnostic procedures. MCP-1 serum levels were determined using a sandwich-enzyme-linked immunosorbent assay. In each patient, the coronary risk factors (CRF), such as hypertension, high cholesterol, diabetes mellitus, obesity, positive family history, and smoking were evaluated. Low-density lipoprotein-cholesterol, lipoprotein(a), and hemoglobinA_1C levels were determined. Patients with CAD proven by angiography had significantly increased MCP-1 levels. In patients without CAD, the increase in MCP-1 depended on the number of CRF. As a marker for endothelial activation the soluble adhesion molecules, soluble intercellular adhesion molecule and soluble E-selectin were measured and both markers were significantly elevated in patients with CAD or multiple CRF when compared with patients without CRF. Although this is not a direct proof, endothelial activation could contribute to elevated MCP-1 levels in atherosclerosis. Conclusion Elevated MCP-1 serum levels could serve as a direct marker of the inflammatory activity in patients at risk for coronary artery and other atherosclerotic vascular diseases. (Circ J 2005; 69: 1484 - 1489)