Background: Anemia was known as a powerful and independent predictor of major adverse cardiovascular events (MACE) in patients with acute coronary syndrome (ACS). The development of anemia during hospitalization for acute myocardial infarction was frequent and was associated with an increased long-term mortality. It has been reported that a decline of hemoglobin concentration during intensive care unit stay in ACS patients without bleeding events was powerful predictor of clinical ischemic events. However there were limited datas available if the decreased hemoglobin level is related to major adverse cardiac events (MACE) after percutaneous coronary intervention (PCI) in ACS patients. Methods: We retrospectively enrolled 211 patients from March 2003 through October 2009. The inclusion criteria was patients diagnosed stable angina or ACS and underwent PCI. Patients were free of blood cell transfusion or bleeding events after PCI. All patients had been checked hemoglobin level 1 day and 2 days after PCI. The 1-year incidences of MACE, including death, myocardial infarction (MI), target vessel revascularization (TVR) and stent thrombosis (ST) were evaluated in all patients included. Statistical analysis was performed using SPSS 18.0. The association between hemoglobin changes and MACE was analyzed with ANOVA. Results: Participated patients were composed of 167 males and mean age was 60.31±10.72. Number of patients diagnosed stable angina were 63, unstable angina were 53, non-ST segment elevation myocardial infarction were 47, and ST segment elevation MI were 42. Initial hemoglobin level was 12.0 to 17.7 g/dL (mean value 13.64±1.19). Hemoglobin change was from -4.1 to +1.8 g/dL 24 hours after PCI and from -4.0 to +1.8 g/dL 48 hours after PCI. Hemoglobin change on 1day after PCI had no significant relation with mortality, subsequent MI, TVR, and ST (p=NS). And hemoglobin on 2day after PCI also had no relation with mortality, subsequent MI, TVR, ST (p=NS). Conclusions: In patients underwent PCI, hemoglobin change day 1 and day 2 after PCI was not related to MACE in stable angina and ACS patients. Therefore routine hemoglobin follow-up after PCI is not needed if patient has low risk of bleeding.