Background and goals of study: Spinal anesthesia using local anesthetics is associated with relatively short duration of action and hence early analgesic intervention is needed in post operative period. Adjuvants are added to improve the quality, to accelerate the onset of action and also to overcome the problems which occur during spinal analgesia. Alpha 2 adrenergic receptor agonist like dexmedetomidine gain the focus of interest for its sedative, analgesic, perioperative sympatholytic and hemodynamic stabilizing properties. Dexmedetomidine is a new highly selective drug among the alpha 2 adrenergic receptor agonist. This study is intended to compare three different doses of intrathecal dexmedetomidine added to hyperbaric bupivacaine for infra umbilical surgeries Methods: Sixty patients were grouped into three groups of twenty each in this randomised, prospective, parallel group, double– blinded study. Patients received 0.5% hyperbaric bupivacaine 2.4ml (12mg) + dexmedetomidine 5 µg, 10 µg or 15 µg in 0.6 ml normal saline. Intraoperative vital parameters, onset and level of sensory and motor blockade, duration of analgesia, postoperative sedation score and rescue analgesic requirement were observed.Results: The mean sensory blockade onset time of 5 µg group was significantly higher than the other two groups. The mean onset time of motor blockade of 15µg group was significantly lower than the other two groups. The duration of blockade and duration of analgesia were significantly higher in the 15µg group. Postoperative sedation score was significantly higher in the 15µg group. Conclusion: Intrathecal dexmedetomidine added to bupivacaine for lower abdominal surgeries, has a dose dependent effect on the sensory and motor blockade, with earlier onset and increased duration of blockade and prolonged post–operative analgesia, better level of sedation and stable hemodynamics.