Abstract: AIM:To observe the effects of early oral administration of different dosages of aspirin and clopidogrel on major adverse cardiovascular events in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI). METHODS: From December 2007 to December 2009, 102 ACS patients treated with PCI were randomly divided into two groups by admission time sequence. For patients in the treatment group (n=54), 300 mg aspirin was given as a draft after admission and then aspirin was orally administered at 300 mg/day for 1 month. After 1 month, aspirin was orally administered at a dosage of 100 mg/day on a long-term basis. Clopidogrel was orally given at 75 mg/day for 1 year after initial dosage of 150 mg/day for 1 week. For patients in the control group (n=48), aspirin was orally given at 100 mg/day on a long-term basis and clopidogrel was orally administered at 75 mg/day for 1 year. Supplementary treatments for patients in both groups were given in the same manner. The occurrence of major adverse cardiovascular events (MACE) was compared, respectively, at 1- and 6-months after PCI. RESULTS: Baseline clinical characteristics in the two groups were basically identical and no statistically significant difference was observed for the distribution of vascular lesions. The incidence rate of MACE of treatment group was lower than control group 1 month after PCI, but the difference was not statistically significant (7% vs. 15%). However, 6 months later, the difference was statistically significant (2% vs. 17%, P<0.05). CONCLUSION: On the basis of general management, increased dosage of aspirin and clopidogrel reduces the occurrence rate of MACE in early treatment of ACS patients undergoing PCI.