Objective: To evaluate whether there is improvement of physiologic response in men with stable coronary artery disease (CAD) receiving percutaneous coronary interventions (PCI) compared to those with syndrome X by cardiopulmonary exercise test (CPX). Method: We prospectively enrolled men with effort angina and ischemic treadmill exercise test or thallium-201 myocardial scan from outpatient department for coronary angiography (CAG) from 2007 to 2009. Patients with advanced valvular heart disease and poor ejection fraction by echocardiography were excluded. According to the result of CAG, they were divided into two groups: those receiving PCI (PCI group) and those without obvious stenosis syndrome X patients (syndrome X group). CPX was carried out before and after CAG with an interval of 4 weeks. A series of physiological parameters were obtained, including age, BMI, lipid profiles, biochemical tests, heart rate, blood pressure, VO2max, VE/VCO2, anaerobic threshold, exercise duration, cardiac output (CO), cardiac power output (CPO), and cardiac reserve. Results: Totally, 20 men, mean age 51.9 year-old, were enrolled in the study. There were significantly lower levels in cardiac reserve and peak exercise CPO before CAG in the PCI patients, but no significant differences between age, BMI, biochemical tests or other parameters obtained from CPX before and after CAG between groups. Conclusion: By CPX, only peak exercise CPO and cardiac reserve before PCI are significantly lower in men with stable CAD, as compared to those with syndrome X. Whether PCI is able to improve CPX remains unclear after this pilot study.