Abstract: Objective To evaluate the effects of dexmedetomidine on postoperative cognitive dysfunction in elderly patients undergoing Transurethral Resection of Prostate.Methods eighty ASA I～II elderly patients scheduled for selective Transurethral Resection of Prostate under general anesthesia,aged 65～85 years,were randomized equally into 2 groups(n=40 each): dexmedetomidine group and control group.In the dexmedetomidine group，a loading dexmedetomidine dose of 0.5μg?kg－1 was infused about 30 min after endotracheal intubation of anesthesia，respectively，followed by infusion a maintenance dose of 0.5μg?kg－1?h-1, respectively,until 40 min before the end of surgery，while the equal volume of normal saline was given in the control group．All patients were tested with mini-mental state examination(MMSE),preoperatively and postoperatively on day 4 and day 7.Results There was no significant difference in the score of MMSE and WMS between dexmedetomidine group and control group preoperatively(P＞0.05).Compared with control group, the score of MMSE in dexmedetomidine group was obviously higher on day 4 and day 7 postoperatively,which was significantly different(P＜0.05). Conclusion dexmedetomidine can reduce the incidence of postoperative cognitive dysfunction in elderly patients undergoing Transurethral Resection of Prostate.