Background: Diabetes is one of the independent risk factors that play an important role in the development of cardiovascular diseases. In the present study, the effect of fasting blood glucose levels in diabetic and nondiabetic patients on the mortality of patients admitted to coronary intensive care units with the diagnosis of acute coronary syndrome during hospitalization has been investigated. Methods: Overall 280 (100 female, 180 male) patients admitted to coronary intensive care unit with the diagnosis of acute coronary syndrome were included in the present study. Files of patients were surveyed retrospectively. Patients whose fasting blood glucose level had been recorded were evaluated. The others were excluded from the study. Incuded patients were divided into two groups. i.e. patients whose FBG level was equal to or over 100 mg/dl and those whose levels were below 100 mg/dl. The relation between inhospital mortality of patients and age, HT, blood urea, creatinine, potassium, lipid levels and stasis findings along with fasting blood glucose levels was evaluated statistically. Results: A significant relation was found between first fasting blood glucose level following admission and inhospital mortality (p=0.004). When the patients were divided into two groups i.e. patients whose blood glucose level was under 100 mg/dl and those whose FBG level was at or over 100 mg/dl, inhospital mortality was found to be significantly higher in the latter group (p=0.020). Conclusion: In patients with acute coronary syndrome, hypertension, blood urea levels and the presence of stasis findings at presentation examination as well as fasting blood suger level may serve as significant predictors of mortality.