BACKGROUND: Because development of acute coronary syndrome (ACS) worsens the prognosis of patients with coronary artery disease, preventing recurrent ACS is crucial. However, the degree to which secondary prevention treatment goals are achieved in patients with recurrent ACS is unknown. METHODS: 214 consecutive ACS patients were classified as having First ACS (n=182) or Recurrent ACS (n=32), and the clinical characteristics of these groups were compared. Fifteen patients died or developed cardiovascular (CV) events during hospitalization, and the remaining 199 patients were followed from the date of hospital discharge to evaluate subsequent CV events. RESULTS: Patients in the Recurrent ACS group were older than those in the First ACS group (76.8±10.8 years vs 68.8±13.4 years, p=0.002) and had a higher rate of diabetes mellitus (DM) (65.6% vs 36.8%, p=0.003). The rate of achieving a low-density lipoprotein cholesterol (LDL-C) level of <70 mg/dL in the Recurrent ACS group was only 28.1%, even though 68.8% of these patients were taking statins. An HbA1c level of <7.0% was achieved in 66.7% of patients with recurrent ACS who had been diagnosed with DM. Overall, 12.5% of patients with recurrent ACS had received optimal treatment for secondary prevention. CV events after hospital discharge were noted in 37.9% of the Recurrent ACS group and 21.2% of the First ACS group (log-rank test: p=0.004). However, recurrent ACS was not an independent risk factor for CV events (adjusted hazard ratio: 2.09, 95% confidence interval: 0.95 to 4.63, p=0.068). CONCLUSION: Optimal treatment for secondary prevention was not achieved in some patients with recurrent ACS, and achievement of the guideline-recommended LDL-C goal for secondary prevention was especially low in this population.