Background: Spinal anesthesia is often used for both elective and emergency surgeries. Anesthesia-related mortality is decreased when general anesthesia is avoided. Aim: To compare the anaesthetic behaviour and haemodynamic consequences produced by the intrathecal injections of plain and hyperbaric solutions of Bupivacaine with the patients in supine horizontal position. Materials and methods: Sixty patients of ASA I – II were divided into 2 groups of 30 each. Group-A was given 3 ml. of -0.5% plain Bupivacaine sub arachnoidally whereas Group-B was given 3 ml. of 0.5% hyperbaric Bupivacaine. Results: It was found that extent of sensory blockade was much higher in Group-B as compared to Group-A. The degree of motor blockade was also much more intense in Group-B as compared to Group-A. The duration of analgesia was more in Group-A as compared to Group-B, but the time onset of analgesia was faster in Group-B (hyperbaric). Haemodynamically patients in Group-A were stable due to lesser extent of sympathetic blockade when compared to patients in Group-B. Conclusion: Plain Bupivacaine gives a lesser cephalad spread and can be effectively used for lower limb surgeries, it has to be used with caution for lower abdominal surgery as the spread is relatively unpredictable.