The aim was to clarify whether CYP2C19 polymorphism is associated with the development of coronary artery disease (CAD). This study enrolled 723 patients with CAD (men 71%, 70 years) and healthy subjects undergoing a medical checkup (n = 453) as controls (men 69%, 53 years). We analyzed the incidence of CYP2C19 polymorphism and its association with the development of CAD in the absence of diabetes, dyslipidemia, and chronic kidney disease to minimize the influence of conventional coronary risk factors. In the analysis without risk factors, there was no difference in the incidence of the CYP2C19 genotype between CAD (n = 115) and control (n = 194) groups [extensive metabolizer, intermediate metabolizer, poor metabolizer (PM) in non-risk CAD: 33%, 46%, 21%, respectively; in non-risk control: 31%, 52%, 17%, respectively]. Analysis between CAD and control groups by the χ test showed that there was significant difference in distribution of CYP2C19 genotype in women alone (P = 0.025) but not in total subjects (P = 0.471) or men (P = 0.678), respectively. CYP2C19 PM was an independent predictor of CAD risk in women alone (odds ratio, 10.717; 95% confidence interval, 1.753-65.505; P = 0.010) but not in men. CYP2C19 PM status might be associated with the development of CAD as a disease susceptibility gene, especially in women.