Background: Various adjuvants have been used with local anaesthetics in spinal anaesthesia to prolong the postoperative analgesia.Dexmedetomidine, alpha2-agonist is now being used as a neuraxial adjuvant The aim of the present study was to compare the block characteristics of dexmedetomidine 5mcg and buprenorphine 75 mcg as adjuvants to 0.5% hyperbaric bupivacaine spinal anaesthesia in infra-umbilical surgeries. Methods and Material: Sixty four patients scheduled to undergo infra-umbilical surgeries were randomly allocated to receive either 12. 5mg hyperbaric bupivacaine plus 5mcg dexmedetomidine (group D, n=34) or 12.5 mg hyperbaric bupivacaine plus 75mcg buprenorphine (group C,n=34) intrathecally Statistical Analysis Used : Chi-square test and student t test was used where applicable to determine whether there was a statistical difference between the groups in the parameters measured .P less than 0.05 was considered as statistically significant. Results: Patients in group D had significantly longer regression of sensory and motor block time than patients in group B. The two segment regression time was 134 ±34.76 min in group D and 106.26 ± 43 min in group B (P<0.05). The regression to Bromage 0 was 330 ± 68 min in group D and 253 ± 58 min in group B  ( P<0.05 ). Conclusion : Addition of dexmedetomidine to hyperbaric bupivacaine intrathecally prolongs the regression of sensory and motor blockade, but does not produce appreciable prolongation of postoperative analgesia or reduce the postoperative analgesic requirement when compared to buprenorphine.