ABSTRACT Background & Aim: Phenylephrine induces maternal bradycardia in 50% of mothers when used for prevention and treatment of spinal anaesthesia-induced hypotension during caesarean delivery. Rapid fluid administration immediately after initiation of the spinal block (co-loading) may have a vasopressor sparing effect. Even though phenylephrine infusion was active as a vasopressor, there was a fall in heart rate occasionally as a reflex action, but it was not statistically significant. There was no incidence of bradycardia or change in rhythm. Aim of the study is to assess the efficacy of prophylactic and therapeutic phenylephrine when administered by different methods as a vasopressor. Method: 60 mothers scheduled for elective caesarean section were recruited in this randomized controlled trial. The primigravida included in the study were divided into two groups; group 1 (n = 30) received intravenous prophylactic phenylephrine infusion at 100 micrograms/min for 3 minutes immediately after subarachnoid block and group 2(n = 30) received phenylephrine as boluses of 100 microgram for the treatment of hypotension following subarachnoid block. Vital signs (blood pressure, heart rate, and arterial oxygen saturation) were recorded throughout the surgery. Maternal and neonatal perioperative complications were also controlled and recorded. Results: There was an insignificant difference in demographic data between the groups. In Group I, only 6.7% incidence of hypotension episodes, whereas in Group II, 96.7% incidence of hypotension episodes were seen, indicating phenylephrine infusion was more effective in preventing hypotension episodes. In both, the groups had similar pre-induction systolic blood pressure, but the mean systolic blood pressure was higher in the infusion group and was statistically significant. In both groups DBP was higher in the infusion group and was statistically significant. Mean arterial pressure pre-induction was similar in both the groups, but mean arterial pressure was higher in the infusion group and was statistically significant. Phenylephrine does much higher in Group I (infusion group) when compared to Group II (bolus group), which was statistically significant (P-value <0.001).No significant side effects were observed in the study (nausea, vomiting). There was no significant difference between the two groups in APGAR score.