Background : Intrathecal adjuvants have gained popularity with the aim of prolonging the duration of block, quality of block and decreased resource utilization compared with general anaesthesia. In present study, we studied onset and duration of sensory and motor block as well as adverse effects of adding Dexmedetomidine (5µg) as an adjuvant to intrathecal 0.5% heavy bupivacaine and of intrathecal 0.5% heavy bupivacaine alone for lower limb surgeries. Method : This was a prospective, randomised control study conducted in 90 Patients of ASA grade I and II undergoing elective surgeries under spinal anaesthesia .The patients were randomly allocated to two groups of 45 each to receive intrathecally either 15 mg (3ml ) hyperbaric bupivacaine alone(group B) or 5µg (group D5) of dexmedetomidine added to 15 mg hyperbaric bupivacaine. The onset time to reach T10 sensory and Bromage 3 motor level, the regression time for S1 sensory and Bromage 0 motor block, Sedation scores, hemodynamic changes and side effects were recorded. Results: It was concluded from present study that in Dexmedetomidine group time to reach T10 sensory blockade and complete motor blockade was earlier and a higher level of sensory blockade compared to control group achieved. Duration of sensory, motor blockade and duration of analgesia was significantly prolonged in the Dexmedetomidine group compared to the control group. Conclusions: Intrathecal low dose Dexmedetomidine in a dose of 5µg along with 0.5% hyperbaric bupivacaine is a better adjuvant for spinal anaesthesia in patients undergoing elective lower limb surgeries