Background: Only a few studies presented concerning anemia because of its association with myocardial ischemia, and demonstrated that anemia is an independent predictor of high 30-day major adverse cardiac events (MACEs) and 1-year MACEs after percutaneous coronary intervention (PCI). The aim of this study is to elucidate if the sustained anemia is associated with poor long term clinical outcomes. Methods: Anemia was defined by WHO criteria (hematocrit below 36% for female and below 40% for male subjects). Laboratory study was performed at the index drug-eluting stent (DES) implantation and at the outpatient visit between 3moths and 12months later. We categorized patients into four groups based on initial and follow-up hematocrit levels (normal, corrected anemia, newly developed anemia, uncorrected anemia groups). Results: We analyzed consecutive 6749 patients performed PCI with DESs in COACT (CathOlic medical center percutAneous Coronary inTervention) registry from January, 2004 to December, 2009. Of these, 3555 subjects with initial and follow-up hematocrit were enrolled in this study and median follow up was 24짹19 months. After adjusting multiple covariates including age, sex, body mass index, hypertension, dyslipidemia, family history of coronary artery disease, history of ischemic heart disease, serum creatinine (>2.0 mg/dL), and initial ejection fraction by echocardiography, newly developed anemia group and uncorrected anemia group demonstrated a significant increase in a hazard ratio (HR) of a composite of death and myocardial infarction (HR=2.358, p=0.004, 95% confidence interval (CI) 1.321 to 4.209; HR=1.875, p=0.047, 95% CI 1.008 to 3.486, respectively) comparing with normal group. There was no significant increase of HR in the corrected anemia group (p=0.591, 95% CI 0.636 to 2.215). Conclusions: Follow-up anemia after PCI is a poor prognostic factor. Concerning MACEs, follow-up anemia is more important than anemia at the index procedure, which should be corrected.