Abstract : Spinal anaesthesia is the most popular regional anaesthesia technique for lower limb orthopaedic and lower abdominal surgery. Localanaesthetic agents as sole doesn’t have the advantage of postoperative prolonged analgesia. Nalbuphine being an opioid agonist antagonist was studied as adjunct to intrathecal Bupivacaine in different doses by different authors. We have decided to study intrathecal Nalbuphine 0.5 mg added to Bupivacaine against plain Bupivacaine. We conducted study to know effectiveness of intrathecal Nalbuphine on characteristics of subarachnoid block such as sensory block, motor block and postoperative analgesia. After randomization Group A patient received intrathecal Bupivacaine 0.5% heavy whereas Group B patients received intrathecal Bupivacaine 0.5% heavy with Nalbuphine 0.5 mg. Sensory and motor onset characteristics are significantly faster in Group B as compared to Group A. Duration of analgesia was significantly prolonged in Group B as compared to Group A with significantly less number of post operative analgesic requirement. Side effects are minimal and easily treatable in both groups. We recommend that 0.5 mg Nalbuphine as an adjunct to 0.5% Bupivacaine significantly produce favorable sensory and motor characteristics with good post operative analgesia with negligible side effects.