Background:One of the main causes of maternal mortality among pregnant women is postpartum hemorrhage (PPH). It is clear that uterine atony is the primary cause of death in roughly 45% to 55% of cases. The present study assessed effect of administration of different doses of phenylephrine with oxytocin on the prevention of oxytocin induced hypotension in caesarean section under spinal anaesthesia.Materials & Methods: 60 females were divided into 3 groups of 20 each. Group I patients received oxytocin 3U and phenylephrine 50 µg diluted to 10 cc with normal saline as an infusion over 5 minutes, group II patients received oxytocin 3U and phenylephrine 75 µg diluted to 10 cc infusion over 5 minutes and group III patients received oxytocin 3U and normal saline diluted to 10 cc infusion over 5 minutes. In each group, the following variables were measured and compared: height, weight, sensory block, length of operation (minutes), time spent extracting the infant from induction and skin incision (minutes), incidence of hypotension, and dose of rescue vasopressor administered. Results:The mean age in group I was 26.2 years, in group II was 26.4 years and in group III was 25.1 years. The mean height was 163.2 cm in group I, 162.5 cm in group II and 165.1 cm in group III. The mean weight was 67.4 kgs in group I, 68.2 kgs in group II and 66.5 kgs in group III. The difference was non- significant (P> 0.05). The duration of surgery was 46.3 minutes in group I, 47.2 minutes in group II and 45.8 minutes in group III. Extraction time of baby from induction was 11.8 minutes, 11.9 minutes and 12.4 minutes and extraction time of baby from skin incision was 7.5 minutes, 8.4 minutes and 8.5 minutes in group I, II and III respectively. The difference was non- significant (P> 0.05). Dose of rescue vasopressor given (µg) was 40.3, 8.7 and 87.2. Incidence of hypotension was seen in 11, 4 and 15 group I, II and III respectively. MAP before oxytocin infusion was 82.2, 83.2 and 78.2 and MAP after oxytocin infusion was 67.2, 76.9 and 66.9 in group I, II and III respectively. Conclusion:In contrast to phenylephrine 50 µg and oxytocin 3U during caesarean sections performed under spinal anesthesia, the results indicated that co-administration of phenylephrine 75 µg and oxytocin 3U lowers the incidence of oxytocin-induced hypotension.