Background: The dexmedetomidine is a highly selective -2 adrenoreceptor agonist and frequently used as an adjuvant to anesthesia for intraoperative hemodynamic stability with infusion doses ranging from 0.2 to 0.7 µg/kg/hr. We have contemplated to study different infusion doses in patients undergoing supratentorial tumor surgery to establish the optimum dose. Methods: Sixty ASA grades I/II patients, aged 20-65 years scheduled for elective surgery were divided randomly into four equal groups (n=15). In groups (2, 3 & 4), dexmedetomidine was infused as a bolus dose of 1 µg/kg over15min after the induction of anesthesia; and was maintained with dexmedetomidine 0.3 µg/kg/ hr (group 2), dexmedetomidine 0.4 µg/kg/hr (group 3) and dexmedetomidine 0.5 µg/kg/ hr (group 4) as a continuous intravenous infusion at the rate of 14ml/hr during perioperative period. Group 1 received normal saline during intraoperative period. Hemodynamic changes, intraoperative brain condition, emergence characteristics and complications during the study period were assessed. Results: Heart rate, systolic, diastolic and mean arterial pressures were significantly lower in dexmedetomidine (group 2, 3 and 4) as compared to control (group 1) (p<0.05). These parameters were comparable in dexmedetomidine groups. Blunting of tachycardia response to intubation and the hypertensive response to extubation were observed in these patients. Intra-operative brain relaxation scores as assessed by surgeons were comparable in all four groups (p>0.05). Opioid sparing effect was seen with dexmedetomidine groups in terms of better hemodynamic stability even at lower doses. Incidence of bradycardia was 13% and hypotension was 20% which were higher in Group 4 but incidence was statistically comparable with other groups. Similarly, 3(20%) patients could not be extubated due to poor cough reflex and sedation. They were shifted to ICU for elective ventilation. Conclusions: Dexmedetomidine attenuates stress responses to various noxious stimuli during surgery, maintains hemodynamic stability, blunts tachycardia and hypertensive response, reduces requirements of opioids and provide good intraoperative brain conditions and early recovery. The benefit risk assessment favors an initial bolus of 1µg/ kg over 15 min followed by an infusion of 0.4 µg/kg/hr over other doses (0.3 µg/ kg/hr and 0.5 µg/kg/hr) in patients undergoing supratentorial tumor surgery.