BACKGROUND Nowadays, early detection and treatment can often keep chronic kidney disease patients from getting worse and prevent the occurrence of cardiovascular disease. Cystatin C (Cys-C) is a new marker for renal dysfunction. This study investigated whether Cys-C played an important role for screening coronary artery disease. METHODS The consecutive 88 outpatients (51 males and 37 females), who were suspected of having effort angina pectoris or asymptomatic ischemic heart disease, were enrolled. Serum Cys-C, which was obtained within 3 months before coronary angiography, was assessed with the presence or absence of coronary arteriosclerosis, the number of culprit arteries, and blood biochemical parameters. RESULTS Mean serum Cys-C was 0.82+/-0.29 mg/l. Significant differences in the estimated creatinine clearance (p=0.036), hemoglobin A1c (p=0.01), left ventricular ejection fraction (p=0.01), creatinine (p=0.007), Cys-C (p=0.006), and high-density lipoprotein (HDL) cholesterol (p=0.001) were observed between the patients with or without coronary arteriosclerosis. Serum Cys-C was significantly greater in the multi-vessel disease (MVD) group than the 0 vessel disease (0VD) group (p<0.001). HDL cholesterol was significantly lower in the MVD group than the 0VD and single-vessel disease groups (p=0.002 and p=0.005, respectively). CONCLUSIONS The results of this study suggest Cys-C might be one of the risk factors for coronary arteriosclerosis in the patients with suspected ischemic heart disease without any history of coronary artery disease. Cys-C was a useful marker to detect coronary artery disease and the level of Cys-C could reflect the severity of coronary arteriosclerosis.