This study is designed to investigate the epidemiologic, genetic, laboratory and clinical characterization of individuals with coronary artery disease. The study group will consist of consecutive patients who are undergoing coronary angiography for suspected coronary artery disease. The diagnosis of coronary artery disease will be confirmed by coronary angiography performed with the Judkins technique using a quantitative coronary angiographic system. Coronary artery disease will be considered to be present if there is a diameter stenosis of at least 50% in at least one of the three major epicardial coronary arteries. The number of diseased vessels will be determined and a classification of 1-, 2-, and 3-vessel disease will be used. Coronary artery segments will be defined according to the Coronary Artery Surgery Study classification. Blood samples from vein and coronary artery will be collected. We will study coronary arteriovenous difference of various markers. Urinary samples will be obtained the day of coronary angiography. We will explore the environmental (including family history, life style, diet, physical activity, neuropsychological functioning，plasma levels of oxidative stress factors, angiogenic factors, and inflammatory markers, etc.) and genetic (including oxidative stress factors and inflammatory factors, etc.) risk factors. We will study the association between various environmental risk factors with the clinical characterization and correlation between the genetic polymorphisms and the presence of coronary artery disease.