Aim: To compare the efficacy of 2 different doses of intrathecal Buprenorphine (45 mcg and 60 mcg) with Levobupivacaine in patients undergoing elective lower limb orthopaedic surgeries. Materials and Methods: This randomized double blind controlled study was conducted at IMS and SUM Hospital from March 2020 to April 2021 among 60 patients divided into group I and II of 30 each randomly by computer generated random numbers who were posted for elective lower limb surgeries after obtaining ethical committee approval. Parameters recorded were onset of sensory block and motor blockade, duration of analgesia, haemodynamical changes (HR, SBP, DBP and MAP) and SpO2 was monitored: at baseline, 5 min, 15 min, 30 min, 45 min and 60 min, VAS Score, Sedation score and other side effects (like postoperative nausea and vomiting, pruritis and urinary retention) were monitored at 1st hour, 6th hour, 12th and 24 hours and data were recoded. Results: It was found that the duration of effective analgesia was statistically significant on increasing the dose of Buprenorphine from 45 mcg to 60 mcg. Patients in both the groups were hemodynamically stable throughout the procedure except 2 episodes of diastolic hypotension in group II but patients did not require vasopressors at any point of time during the surgery. There was no statistically significant side effects in both the groups. Conclusion: Buprenorphine at a dose of 60 mcg in comparison to a dose of 45 mcg when added as adjuvant to isobaric Levobupivacaine for spinal subarachnoid block for lower limb surgeries produces longer duration of postoperative analgesia without much significant adverse effects.