Background: Atherosclerotic renal artery stenosis (RAS) was recognized as a major co-morbid condition for patients with cardiovascular disease and frequently unrecognized contributor to refractory hypertension (HTN), ischemic nephropathy and cardiac destabilization syndromes. Also presence and severity of incidental RAS has been known an independent predictor of mortality regardless of the treatment of underlying coronary artery disease (CAD). Although atherosclerotic RAS and CAD arise from the same multiple risk factors and the prevalence of RAS has been reported as 13.5-18% in suspected CAD undergoing coronary angiography, there is little information available about the prevalence of RAS and risk factors in Korean populations. Therefore, we investigated the prevalence and predisposing factors of RAS in patients who underwent coronary angiography (CAG). Methods: This study included 365 patients who underwent CAG and renal angiography simultaneously from Jan. 2007 to Dec. 2008. A renal artery ���50% stenosis on renal angiography was considered as significant RAS. A CAD with at least one stenotic lesion ���70% was considered as significant. Results: Overall prevalence of renal artery atherosclerosis was 14.8% (54 patients). Significant RAS was found in 21 patients (5.75%). Significant RAS was more common in patients with significant CAD (10.38% vs 3.86%, p<0.05) and high blood pressure (8.78% vs 2.16%, p<0.05). Patients with RAS were more likely to be older than patients without RAS (69.81 vs 60.55, p<0.001). Also patients with RAS showed higher serum creatinine (1.181mg/dL vs 0.843mg/dL, p<0.001), blood urea nitrogen (BUN) (24.38 vs 16.04, p<0.05) and lower estimated glomerular filtration rate (eGFR). In multivariate analysis, older age and high BUN level were independent predictors of significant RAS. Conclusion: Simultaneous renal angiography undergoing CAG could be a feasible and reasonable tool for screening RAS in patients with significant CAD, old age, HTN, low eGFR and high BUN.