Intrathecal midazolam for use as a post-operative analgesic when given alone and in conjunction with intrathecal diamorphine was assessed. Fifty-two patients scheduled for elective Caesarean section under spinal anaesthesia were randomly allocated to receive either bupivacaine (B), bupivacaine with diamorphine (BD), bupivacaine with midazolam (BM) or all three (BMD) by intrathecal injection. Post-operatively, no differences in visual analogue score (VAS), sedation or post-operative nausea and vomiting (PONV) could be demonstrated between groups. Patient-controlled analgesia system (PCAS) usage was significantly greater in group B when compared with the other groups. Pruritus was commoner in patients receiving diamorphine (BMD & BD). No side effects attributable to midazolam were identified. Intrathecal midazolam at this dose appears safe and has clinically detectable analgesic properties. The duration of useful analgesia appears to be short-lived.