['This study was to examine the association between plasma retinol binding protein 4 (RBP4) levels and the complexity of angiographic coronary lesion in patients with coronary artery disease (CAD).', 'A cross-sectional and prospective study was carried out in Guangzhou Chinese population. 672 persons were evaluated by medical history, clinical examination, coronary angiography, and fasting plasma samples, and were followed prospectively for 3 years. We measured the plasma RBP4 levels in 447 women (201 with stable CAD and 246 with acute coronary syndrome [ACS]). Coronary lesions were classified as having a simple or complex appearance based on the visual estimation of the coronary angiograms. Median plasma RBP4 levels were significantly higher in stable CAD patients with complex coronary lesions (n\xa0=\xa084) than in those with simple lesions (n\xa0=\xa0117) (38.78[range 32.65-46.91] vs. 30.78 [range 24.48-36.08] μg/ml, P\xa0<\xa00.001). Multiple logistic regression analysis demonstrated that higher RBP4 levels were independently associated with a 23% higher risk for complex lesions (odds ratio 1.228, 95% confidence interval [CI] 1.061 to 1.358; P\xa0=\xa00.031). Among the ACS patients, who had higher RBP4 levels than the stable CAD patients, those with multiple complex lesions had significantly higher median RBP4 levels than those with a single complex lesion (46.47\xa0μg/ml [range 37.68-53.29] vs. 38.15\xa0μg/ml [range 32.26-44.56], P\xa0<\xa00.001). Total plasma RBP4 levels were predictors of cardiac death (hazard ratio [HR]: 1.102; 95% CI: 1.086 to 1.191; P\xa0=\xa00.012) after adjustment for traditional risk factors for CAD.'] Is circulating retinol binding protein 4 associated with coronary lesion severity of patients with coronary artery disease?