OBJECTIVES: This study compared the real-world practice patterns for ACS patients with and without DM in a large privately insured population.  METHODS: A retrospective cohort study was conducted using the MarketScan claims database.  Patients aged 18-65 years (N=22,693), hospitalized with a primary diagnosis of ACS between January 2005 and December 2006 were categorized into 2 groups: with DM (N=6,049) and without DM (N=16,644).  Patient characteristics, treatment patterns during the index-hospitalization and cardiovascular medications use 12-month pre- and post-index hospitalization were analyzed.  Results had p<.0001 unless otherwise stated.  RESULTS: Patients with DM were more likely to be older (56.2 vs. 54.5), female (33.7% vs. 26.6%) and have higher rates of previous MI (14.5% vs. 10.5%), congestive heart failure (13.5% vs. 3.2%), PAD (9.9% vs. 3.7%), TIA/stroke (4.8% vs. 2.0%), hypertension (53.1% vs. 34.1%), hyperlipidemia (42.3% vs. 30.8%) and renal diseases (8.5% vs. 1.2%).  During the index-hospitalization, patients with DM underwent less PCI (42% vs. 51.7%), more CABG (11.6% vs. 8.2%), and were more likely to be medically managed (46.3% vs. 40.1%).  More ACE inhibitors (pre: 40.6% vs. 15.5%; post: 65.2% vs. 60.5%), beta blockers (pre: 38.4% vs. 21.8%; post: 88.4% vs. 85.9%) were prescribed to patients with DM both in the pre- and post-index hospitalization period.  While more statins (59.6% vs. 30%) and thienopyridine (14.6% vs. 6.4%) were prescribed to patients with DM in the pre-period, in the post-period statin use was similar for patients in both groups (89.1% vs. 88.0%, p=0.11) and thienopyridine use was less frequent in patients with DM (72.1% vs. 75.9%) possibly due to higher rates of CABG. CONCLUSIONS: Patients with DM had a less-favorable comorbidity profile, underwent less PCI but more CABG and were more likely to have medical management during the index hospitalization.  Hospitalization with ACS shifted the usage pattern of cardiovascular medications.