Objective To investigate the effect of intensive insulin therapy in critically ill elderly patients.Methods Elderly patients ( ≥ 65 years) admitted to the ICU of Beijing Tongren Hospital from June 2005 to December 2007 were divided into Group A ( glucose control target was 4.4-6.1mmol/L) and Group B ( glucose control target was 7.3-8.3mmol/L).Blood glucose level was controlled with a computer-assisted glucose control protocoL Results A total of 639 patients were enrolled,of which 280 were in Group A and 359 in Group B.The mean blood glucose level of the 2 groups was (6.07 ± 0.56) mmol/L and (7.52 ± 0.87 ) mmol/L respectively,both within the target ranges.The hyperglycemic index was (0.69±0.44) mmol/L in Group A and ( 1.60 ±0.73) mmol/L in Group B (P =0.000).No hypoglycemia adverse events occurred in either group.No significant differences were observed in the length of stay in ICU,duration of mechanical ventilation,hospitalization expenses,ICU mortality,and hospital mortality of the 2 groups.Conclusion Maintaining the blood glucose level of critically ill elderly patients at ≤8.3 mmol/L is safe and practical.