Abstract: Comparing the effects of isobaric and hypobaric bupivacaine in lateral decubitus position. With operative side up, patients randomly received, 3 mL (15 mg) spinal injection of bupivacaine mixed with 2 mL of either normal saline (isobaric) or distilled water (hypobaric). Sensory level and degree of motor block were evaluated on nondependent and dependent sides. Hemodynamic changes were noted. In the hypobaric group, there was a prolonged time to sensory regression to L2 on the operative side; no difference in quality of motor block was noted. Hemodynamic changes were comparable. Spinal hypobaric bupivacaine is superior to isobaric.