Abstract: Objective To study the effect of propofol and midazolam on memory during target control infusion for sedation. Methods Forty healthy male volunteers were randomly devided into 4 groups, all subjects received target controlled infusion with propofol or midazolam for sedation.Group 1 and group 3 were sedated to OAA/S 1 or OAA/S 3, respectively,by using propofol ; group 2 and group 4 was sedated to OAA/S 1 or OAA/S 3, respectively by using midazolam. All subjects learned a list of words before sedation and at the different sedation depths predicted. After recovery the explicit and implicit memory were tested using word stem completion method and process dissociation procedure . Results Compared with 0, there was no significant difference in explicit memory among all the 4 groups. While there was significant difference in implicit memory for group 3 and 4,and there was no significant difference in implicit memory for group1 and group2. Conclusion Sedative-hypnotic drugs not only deepen sedation,but also impair memory as serum concentration increases during target infusion .Drug-induced amnesia is independent of sedation .Propofol and midazolam have the same efficacy on memory at the same sedation scale.