Spinal anaesthesia is the most commonly employed technique in surgeries below umbilicus. The commonly used local anaesthetic is hyperbaric bupivacaine, disadvantage of which is  their short duration of action and early requirement of rescue analgesia post operatively. Alpha–2 agonists like clonidine have been proven to enhance the quality and duration of spinal anaesthesia.  In this study we have used dexmedetomidine, higly selective alpha–2 agonist with a high ratio of alpha2/alpha1 activity .MATERIALS AND METHODS – Ninety patients  randomized into three groups; each group containing thirty patients. The  patient received 3.0 ml of hyperbaric bupivacaine plus either 0.5ml of 5 microgram dexmedetomidine (group D1) ,10 microgram dexmedetomidine (group D2) or  0.9% normal saline (group C). RESULTS – dexmedetomidine prolonged the time to two segment regression, motor regression to bromage 0 and the time to rescue analgesic. All these effects were in the order D2 > D1 > C and statistically significant(p<0.005). All patients were hemodynamically stable. CONCLUSION – Intrathecal dexmedetomidine 5mcg and 10 mcg prolongs anesthetic and analgesic effects of hyperbaric bupivacaine and 10 mcg dose is more beneficial for prolonged surgeries.