Objective: To survey the prevalence and risk factors for aspirin resistance in patients undergoing percutaneous coronary intervention. Methods: Cross-sectional study was conducted at Heart Institute in Ho Chi Minh city from 12/2011 to 6/2012 on patients with percutaneous coronary intervention A loading dose of 325mg aspirin was used in patients with acute coronary syndrome before undergoing urgent coronary intervention, and patients with chronic coronary disease received standard dose of 100mg aspirin/day at least 4 days before undergoing intervention. After the intervention, all patients receive 250 mg aspirin /day. Platelet function were measured about 48 hours after the intervention with PFA 100 test (Platelet Function Analyzer 100) by cartridge collagen/epinephrine (CEPI). Results: In 174 patients included in the study, there were 37 cases (21,3 percent) resistant to aspirin therapy. Some factors significantly relating to aspirin resistance (p0.05) were chronic kidney disease, obesity, myocardial infarction with ST segment elevation and ischemic cardiomyopathy. Conclusions: Aspirin resistance frequency is relatively high in patients with percutaneous coronary intervention.