BACKGROUND: The impact of diabetes in patients with acute myocardial infarction (AMI) treated with primary percutaneous coronary intervention (PCI) is unclear. The benefit of abciximab in this subset of patients remains controversial. METHODS AND RESULTS: Three hundred and twenty-seven consecutive and unselected patients with acute AMI treated with primary PCI were included in our single-center retrospective registry, 103 diabetic (31%) and 224 nondiabetic (69%). Abciximab was given at the physician's discretion. Diabetic patients were older (mean age 68.5±11 vs. 65±12 years; P=0.009), had an increased prevalence of hypertension (73 vs. 54%; P=0.001), a decreased prevalence of smoking (31 vs. 45%; P=0.02), a longer duration of symptoms before hospital admission (190 vs. 143 min; P=0.031), and a higher number of stents implanted (1.4 vs. 1.2; P=0.04). Other clinical and angiographic characteristics were comparable in the two groups. Diabetic patients had a higher incidence of the combined end-point of death and reinfarction rate at 30 days (18 vs. 10%; P=0.04) compared to nondiabetic patients. Abciximab treatment was associated with a lower in-hospital (23.8 vs. 5%; P=0.005) and 30-day (23.8 vs. 6.6%; P=0.012) mortality, and a lower incidence of death and reinfarction at 30 days (33.3 vs. 9.8%; P=0.003) in diabetic patients. In nondiabetic patients, abciximab was not associated with improved outcome measures. Advanced Killip class (III and IV) and abciximab were found to be independently associated with 30-day death or myocardial infarction [respectively, odds ratio (OR) 6.075, 95% confidence interval (CI) 1.59-23.218, P=0.008 and OR 0.177, 95% CI 0.034-0.938, P=0.042] in the propensity score-matched populations of diabetic patients. Advanced Killip class and thrombolysis in myocardial infarction score index were found to be independently associated with 30-day death or myocardial infarction (respectively, OR 6.607, 95% CI 1.5-29.106, P=0.013 and OR 1.094 95% CI 1.042-1.148, P