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Midazolam, the only clinically available water-soluble benzodiazepine, has been reported to have an antinociceptive effect through neuroaxial pathway. Also it can be used epidurally for postoperative analgesia and chronic pain management. In a recent study it was disclosed that when midazolam was added to intrathecal bupivacaine it improved the duration and quality of the spinal anesthesia. In this study the effects of this drug on intraoperative motor and sensory blocks were evaluated.We studied 53 adult ASA I and II patients scheduled for elective lower-limb surgery. All patients received epidural anesthesia with 19 ml of lidocaine and l ml additive. Patients were randomly allocated to three groups. Midazolam was administered epidurally in doses of 5 mg (1 ml) and 3 mg (1 ml) in groups land 2 respectively, and group 3 received normal saline Iml as placebo. Patients were evaluated for the onset time and duration of sensory and motor blocks, duration to the first rescue analgesic and hemodynamic changes.Onset of sensory block and time to peak effect was significantly faster and shorter in group one patients who received 5 mg midazolam as compared with those of other two groups (P = 0.002 and P = 0.001, respectively). Also, the durations of motor and sensory blocks were significantly longer in group one compared with those of other two groups (P = 0.004 and P = 0.045, respectively).Midazolam can improve the durations of sensory and motor blocks of lidocaine in a single epidural administration. It seems that the 5 mg dosage works better than the lower one.