Background: Various adjuvants are co-administrated with local anaesthetic agent to improve the speed of onset of block, duration of analgesia and can decrease the dose of local anaesthetic agent. As the dose of local anaesthetic decreases, its adverse drug reaction also used to decrease specifically Bupivacaine. Present study has been designed to evaluate the, efficacy and safety of dexmedetomidine as an adjuvant to bupivacaine in spinal anaesthesia. Method: This is a randomised, double blind, prospective comparative study conducted in the department of anaesthesia, Based on inclusion and exclusion criteria 72 patients were enrolled for this study. These patients were randomly allocated in to two groups Group B and Group BD. Sensory parameters like, onset of sensory block; total duration of sensory block was recorded using pin prick method. Motor block was assessed with modified Bromage score. Time for onset and duration of motor block was recorded. Result: Mean time required for the onset of sensory block in group B was 3.24 + 1.34min and in Group B, it was 2.42 + 0.84 min. This difference is statistically significant. The P value was 0.006. The mean duration of sensory block was 181.07 + 20.8 min in group B and 263.6+38.8 min in group BD. This difference was significant statically (p=0.00001). The mean time for onset of motor block was 8.31 + 1.84 min in group B and 7.94 + 32.0 in group BD. This difference is not significant statistically. The p value was 0.1428. Discussion and Conclusion: From present study we conclude that 5 microgram dexmedetomidine as an adjuvant to hyperbaric bupivacaine prolong the duration of sensory and motor block. It provides good quality of analgesia, haemodynamic stability and prolongs post-operative analgesia.