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BACKGROUND Neuraxial anaesthesia is most widely practiced for surgeries of lower abdomen and lower limbs. Hyperbaric bupivacaine along with adjuvants are used with an intention to prolong the duration and quality of sensory and motor block with minimal side effects. The aim of the study was to compare intrathecal dexmedetomidine and magnesium sulphate as adjuvants to bupivacaine in patients undergoing lower abdominal and lower limb surgeries. METHODS 90 patients of either sex, in the age group of 18-60 years and ASA grade I and II posted for lower abdominal and lower limb surgeries were randomly allocated into three groups of 30 each. Group B: (n= 30) received intrathecal injection of a solution containing 15 mg of 0.5% bupivacaine (hyperbaric) and 0.1 ml of normal saline. Group D: (n= 30) received intrathecal injection of a solution containing 15 mg of 0.5% Bupivacaine (hyperbaric) and 5 mcg of Dexmedetomidine. Group M: (n= 30) received intrathecal injection of a solution of 15 mg of 0.5% bupivacaine (hyperbaric) and 50 mg of magnesium sulphate. Each one of the solutions was made to a total volume of 3.1 ml. The time of onset to reach peak sensory and motor level, the regression time for sensory and motor block, hemodynamic changes and side-effects were recorded. ANOVA/Kruskal Wallis test, Post Hoc Tukey's test, Mann Whitney test, Chi-Square test /Fisher's exact test were applied for interpretation of data. RESULTS The mean time to onset of sensory block was significantly faster in group D (5.47 ± 1.81 min) than group B (6.73 ± 1.53 min) and group M (8.8 ± 1.54 min). The mean time to onset of motor block was rapid in Group D (5.92 ± 1.48 min) and delayed in Group M (8.8 ± 1.54 min) in comparison with the control Group B (6.33 ± 1.37 min). The mean duration to S2 segment regression was significantly higher in group D (323.27 ± 21.38 min) and group M (269.53 ± 12.18 min) than group B (203.1± 12.13 min). The mean time for total duration of motor block was prolonged in Group D (287.27 ± 19.22 min) and Group M (238.53 ± 11.84 min) when compared with the control Group B (168.77 ± 9.7 min). The patients were haemodynamically stable during the surgery with statistically insignificant adverse events. CONCLUSIONS Dexmedetomidine has faster onset of sensory and motor blockade with prolonged duration of analgesia than magnesium sulphate. Both can be used as effective adjuvants to intrathecal hyperbaric bupivacaine with insignificant adverse events.