BACKGROUND: Benzodiazepines acting on the GABA receptor complex in the spinal cord are known to induce antinociception. In the present study we aimed to evaluate the effect of intrathecal midazolam with bupivacaine following hemorroidectomy. METHODS: Forty five patients were involved in this study. Patients were randomly allocated to one of 3 groups: the control group received 0.5% heavy bupivacaine 5 mg and 0.9% NaCl 0.2 ml intrathecally, group BM1 0.5% bupivacaine and midazolam 1 mg (0.2 ml), group BM2 0.5% bupivacaine 5 mg and midazolam 2 mg (0.4 ml), respectively. The analgesic effects and side effects were compared among the 3 groups. RESULTS: There was a significant difference among the 3 groups in time-to-first-pain medication and total consumption of analgesics during the 24 h after surgery. Furthermore, the analgesic effect of midazolam was dose-dependent: 2 mg of midazolam showed better results than 1 mg. All the patients showed no considerable side effects. CONCLUSIONS: We conclude that intrathecal midazolam caused a significant delay in time-to-first-pain medication and reduced utilization of analgesics within 24 h. Therefore, intrathecal midazolam can be used as an effective adjunct for spinal anesthesia for postoperative pain control.