Purpose: The purpose of the present study was to examine the influence of diabetes mellitus (DM) on the clinical outcomes in patients with acute myocardial infarction (AMI) treated with primary coronary stenting within 24h of the onset of symptoms. Methods: we enrolled 100 patients( 50 diabetic and 50 nondiabetic) admitted to the coronary care unit, New Kasr Al-aini teaching hospital and Nasr City Insurance hospital in the period from March 2012 to september 2013 with acute myocardial infarction (AMI) treated with primary coronary stenting within 24h of the onset of symptoms. Clinical outcome was observed in every patient for major adverse cardiac events( MACE) and hospital stay. Also, echocardiography was done before patient’s hospital discharge. Patients were followed up at 3 months for the occurrence of major adverse cardiac events. Follow up was possible in 92 patients (92%). Results: The diabetic patients showed higher incidence of hypertension (p = 0.005) and family history of coronary artery disease (CAD) (p = 0.05) also higher incidence of heart failure (p = 0.049)during admission and higher mean serum creatinine kinase MB mass assay level (p=0.015). There were no statistically significant differences in other variables. Procedural success was similar in the 2 groups. As regard to in-hospital clinical course, diabetic patients were more likely to have early post MI Heart failure (p = 0.009) and hospital mortality (p = 0.027). At 3 months, diabetic patients were significantly more likely to experience recurrent MI (p=0.027), were more likely to be rehospitalized for ACS and decompensated heart failure (p = 0.042), however there was no significant difference in mortality (p=0.072). Conclusion : Compared to nondiabetic, diabetic patients are: more likely to have early post MI Heart failure and hospital mortality. Also, diabetic patients are significantly more likely to experience recurrent MI and are more likely to be hospitalized for ACS or decompensated heart failure.