Introduction: Phenylephrine is the ideal vasopressor for spinal anesthesia in lower segment ceasearen section, this study was undertaken to compare the bolus doses of 50μg of Phenylephrine with a prophylactic fixed infusion rate of 50μg/min of the same drug. Methodology: A prospective randomized, comparative study of 60 parturients scheduled for elective or emergency ceasearean section Patients were randomly assigned into two groups by sealed envelope method (bolus/infusion) group. After recording the baseline vital parameters and preloading with 500 ml Ringer lactate, spinal anaesthesia will be administered .Group A received injection Phenylephrine 50 μg bolus if systolic blood pressure is <20% basal value, bolus was repeated if necessary. Group B were given Phenylephrine 50 μg/min infusion started immediately after spinal anesthesia and continued for 2 minutes and subsequent adjustment was made, Hemodynamic monitoring will be done every minute till extraction of the baby. Results: The present study showed that the mean fall in SBP, DBP, MAP were less in infusion group (p<0.001)compared to bolus group however the fall in HR is more in bolus compared to infusion group (p<0.001) . Conclusion: We conclude that prophylactic phenylephrine infusion leads to a significantly better control of post spinal hypotension compared to Phenylephrine bolus dose.