Introduction: In order to maximize quality of anesthesia and effective analgesia, a number of adjuvants have been added to intrathecal local anesthetics but none of them have yet been identified without any adverse events. Material & Methods: 90 patients scheduled for lower limb orthopaedic surgery under spinal anaesthesia were included in this prospective randomized double blind study. Patients were randomly allocated into any of three groups. Group A– Patients receiving 0.5% hyperbaric bupivacaine 3ml (15mg) + 0.1ml (10µg) dexmedetomidine hydrochloride. Group BPatients receiving 0.5% hyperbaric bupivacaine 3ml (15mg) + 0.1ml (50mg) magnesium sulphate. Group C – Patients receiving 0.5% hyperbaric bupivacaine 3ml (15mg) + 0.1ml normal saline as control. The onset time for sensory and motor block, the regression time for block, duration of effective analgesia, hemodynamic parameters and any adverse events were recorded at timely intervals. Results: The onset time of sensory and motor block was faster with Group A (2.16 and 3.30 min) as compared to Group C (3.72 and 4.88 min), whereas it was significantly prolonged with Group B (6.1 and 7.03 min). Duration of sensory and motor block was significantly prolonged with Group A (344.67 and 318.67 min) and to a lesser extent with Group B (273 and 246 min) when compared to control Group (195 and 169.5 min). The duration of effective analgesia was longer with Group A (375 min) and Group B (294.3 min) when compared with Group C (216 min). Conclusion: Addition of Dexmedetomidine as an adjuvant to hyperbaric Bupivacaine intrathecally leads to rapid onset and prolonged duration of anesthesia. With intrathecal Magnesium sulphate, the onset of block was delayed but the duration of block was prolonged although to a lesser extent. Duration of effective analgesia was prolonged in both the study groups although more pronounced with Dexmedetomidine. Hemodynamic parameters where stable in all the three study groups without any significant group specific side effects.