Introduction:Various adjuvants have been clinically studied for prolongation of intraoperative and postoperative analgesia. Methods:In this randomized,double blind study,120 ASA I/II patients of either sex, age 25–50years undergoing lower limb surgery were selected and randomly allocated into three groups(n=40). In addition to 3ml of 0.75% isobaric ropivacaine , patients of groups A, B and C received 0.9% normal saline (0.5ml), 60mcg Buprenorphine (1:2.5 dilution) and 25mcg fentanyl (0.5ml) respectively (Total volume 3.5ml). Onset time and duration of sensory and motor block, duration of analgesia, hemodynamics,VAS score, sedation score and adverse effects were assessed. Results:The duration of analgesia was longest in Group B (8.30±0.85hrs), followed by Group C (6.03±0.54hrs, P <0.001) and Group A (4.12±0.60hrs, P<0.001). Conclusion:Both intrathecal Fentanyl (25mcg) and buprenorphine (60mcg) produce significantly longer duration and better quality of postoperative analgesia than ropivacaine alone. On comparing, Buprenorphine appeared to be superior to fentanyl.