OBJECTIVES: Re-hospitalization and mortality rates are increasingly being used as quality of care measures that have significant reimbursement implications.  We examine the rates of re-hospitalization and mortality of acute coronary syndrome (ACS) patients in real-world clinical practice. METHODS: Commercially-insured patients (age >18 years) with an inpatient hospitalization for ACS [ICD-9-CM codes for acute myocardial infarction or unstable angina (UA)] between 1/1/2007-5/31/2010 were identified from medical claims in the HealthCore Integrated Research Database (HIRD). Patients with ACS events within one year prior to index hospitalization were excluded.  All-cause and ACS-related re-hospitalizations and mortality rates  within 30 days and 12 months after index event were evaluated. RESULTS: :Of 66,772 ACS patients (60% male; mean age 66.6 years), 21% had diagnostic coding for ST elevation myocardial infarction (STEMI), 31% had coding for non-ST elevation myocardial infarction (NSTEMI), 37% had UA, and 11% had not otherwise specified (NOS) ACS. Approximately, 90% and 52% of patients had >30-days and > 12 months of continuous eligibility respectively.   The 30-day all-cause re-hospitalization rate was 16.3 % (STEMI: 16.4%, NSTEMI: 19.0%, UA: 13.3%, NOS: 20.6%;) and 6.3 % (STEMI: 8.8%, NSTEMI: 6.6%, UA: 5.2%, NOS: 4.5%) for an ACS-related re-hospitalization. The 12-month all cause re-hospitalization rate was 41.3% (STEMI: 39.0%, NSTEMI: 46.4%, UA: 38.2%NOS: 46.6%, )and 16.6% for an ACS-related re-hospitalization.  The 30-day post-index mortality rate was 2.4 % (STEMI:1 .8%, NSTEMI:4.3%, UA:0.5%, NOS:5.2%;) and the 12-month rate was 7.0%. For patients with ages > 65 years, the 30-day all-cause and ACS-related re-hospitalization rates were 21.2% and 7.0%, respectively. CONCLUSIONS: The re-hospitalization and mortality rate for ACS patients within 30 days and 12-months post-index hospitalization discharge as observed in real-world clinical practice remain high. Use of more effective therapies may provide an opportunity to improve important clinical and economic outcomes in ACS patients.