Introduction: Hyperglycemia and insulin resistance are a common occurance incritically ill patients and are associated with adverse outcome. Thus, intensive insulin therapy isadvocated increasingly for hyperglycemic intensive care unit (ICU) patients to redcue morbidityand mortality. Nevertheless convincing evidence of benefit comes mainly from trials carried out on surgical ICU patients while studies of the effects of intensive insulin therapy in mixed medical and surgical ICU patients have yielded conflicting results.Methods: This study aimed at determining the efficacy of tight glycemic control and impact onmorbidity and mortality measures in mixed medical/surgical ICU patients. On admission, sixtypatients were randomly assigned to recive intensive insulin therapy (IIT) (30 patients) usinginsulin infusion (target blood glucose= 90-149 mg/dl) or conventional glycemic control (30patients) (target blood glucose <199 mg/dL). Results: There was no statistically significant difference between both groups in the mean age(41.6+19 vs 50+23.9 years, P= 0.13), sex (P = 0.6), or the presence of history of diabetesmellitus (P = 0.25), but there was statistically significant higher mean APACHE II in (IIT) group(15.5 vs 13.2, P= 0.043). The tight glycemic control group showed a statistically higher mean daily insulin dose (53.1 vs 12.7 units, P< 0.001), higher mean duration of stabilization withintarget blood glucose range (21.8 vs 12.2 hour (P< 0.001) and lower mean blood glucose level (136 vs 166.6, P= 0.004) compared to conventional group. There was no statistically significantdifference between the two groups as regards need for vasopressor use (P = 0.79) or the need for renal replacement therapy (P = 0.71), however, the incidence of acute kidney injury was lower in the tight control group (33.3% vs 53.3%) but lacks statistical significance (P = 0.09). Beneficialeffect significantly was found in the tight glycemic control group regarding incidence of bacteremia (P = 0.037), mean duration of ICU stay (6.6 vs 14.1 days, P= 0.03) and acceleratedweaning from mechanical ventilation (MV) (2.5 vs 8.2 days, P= 0.028). The tight glycemiccontrol medical subgroup showed statistically significant less duration of ICU stay (7.9+3 vs16+4.9, P= 0.05). As regards the study surgical subgroup, tight glycemic control was associatedwith statistically significant lower bacteremia rate (6.7% vs 46.7, P= 0.013), accelerated weaning from MV (0.5 vs 6.6 days, P= 0.009) and lower mean duration of ICU stay (5.3 vs 12 days, P=0.023). There was no statistical significant difference between the two group regarding frequencyof hypoglycemia [tight (16.7%) vs conventional (30%), P= 0.063)]. We found lower mortality rate in the tight glycemic control group (26.7%) compared to conventional group (40%), yet with no statistical significance (P= 0.412). Meanwhile on subgroup analysis, there was statisticallysignificant lower mortality in surgical ICU patients who assigned to receive IIT compared tothose who receive conventional glycemic regimen (6.7% vs 26.7%, P = 0.045). Also, there wassignificant reduction in mortality with IIT among long stayers (> 5 days) compared toconventional group (16.7 vs 33.3%, P = 0.05).Conclusion: Tight glycemic control significantly reduce morbidity in mixed medical andsurgical ICU patients by the prevention of newly acquired bacteremia during ICU course,acceleration of weaning from mechanical ventilation and early discharge from intensive care unitwith insignificant reduction in mortality rate among the whole mixed medical / surgical ICUpatients yet with significant survival beneficial in surgical ICU patients & in mixed group ofpatients who stayed more than 5 days in the intensive care unit.