ObjectiveTo investigate the association of diabetes with ST segment resolution and clinical outcomes after fibrinolysis in patients with first ST elevation myocardial infarction (STEMI). Methods and resultsClinical information from 275 consecutive patients with first STEMI, who received streptokinase within 6h of chest pain initiation, was collected prospectively. ST resolution ≥50%, 90min after fibrinolysis, was considered as a sign of successful reperfusion. Association of diabetes with the risk of reperfusion failure, development of heart failure and in-hospital mortality was determined before and after controlling for other coronary risk factors.ST resolution ≥50% was present in 45.1% of non-diabetics and 48.7% of diabetics (p=0.1). Heart failure and in-hospital mortality were more common in diabetics (25.7% vs. 14.8%, p=0.03 and 17.8% vs. 8.4%, p=0.03, respectively). Diabetics were more likely to have three-vessel disease in coronary angiography (23% vs. 8%, p<0.001). After controlling for baseline characteristics, diabetes was not independently associated with reperfusion failure and major adverse cardiac events, including heart failure and in-hospital mortality. ConclusionsST resolution is not affected by the presence of diabetes. Although diabetics have higher prevalence of heart failure and in-hospital mortality after treatment of STEMI with streptokinase, their poor outcome is most likely due to higher burden of simultaneous coronary risk factors.