Dexmedetomidine is alpha–2 agonist that was approved by FDA in 1999 for use in human as a short term medication for sedation/analgesia in the ICU. It produces sedation and anxiolysis and also prolongs the duration of spinal anaesthesia. The study was conducted in the Department of Anaesthesiology at DR. S.N.M.C, JODHPUR (RAJASTHAN) on 72 patients with 36 in each group. Hyperbaric 0.5% bupiva*caine 12.5mg(2.5ml)was injected intrathecally in all patients.Patients of group D received loading dose of 1mcg/kg/hr dexmedetomidine over 10minutes and maintainance dose of 0.2mcg/kg/hr through intravenous infusion pump till the end of surgery while group C received the same calculated volume of normal saline. Time for the onset of sensory and motor blockade, duration of analgesia, sedation scores and hemodynamic parameters were assessed.  Administration of IV dexmedetomidine during SAB hastens the onset of sensory block and prolongs the duration of sensory and motor block. It provides excellent sedation during surgery .