The purpose of this study is the comparison of intravenous Phenylephrin and Ephedrin to treat hypotension associated with spinal anesthesia in the patients undergoing cesarean section. The study was placed in Ali- ebn- Abitaleb hospital operating room in Zahedan, 2015. A double-blind clinical trial was carried out on 120 patients. Inclusion and exclusion criteria are as follows: Inclusion criteria: 20-35 years old, Elective surgery, ASA class 1, pregnancy, Gestational age 30-36 week. Exclusion criteria : History of primary HTN, cardio-cerebro vascular diseases, Diabetic mellitus, malformation of placenta and umbilical cord, high risk pregnancy, Gestational HTN, Contraindication of spinal Anesthesia. Exclusion criteria during the study: abnormal hemorrhage under surgery, unsuccessful spinal anesthesia, high spinal Anesthesia (at level above T4), more than 75min surgery duration. In the present study, the patients were divided into 4 categories randomly, each including 30 patients. At the first, the patients were received Ringer located 10 cc/kg and then spinal Anesthesia was performed with Bupivacain and Fentanyl. When Hypotension was occurred Ephedrin or Phenylephrine was given as follows: in the first category Ephedrin 5mg, in the second category Ephedrin 10mg, in the third category Phenylephrine 50µg, in the fourth category Phenylephrine 100µg Bolous, and also they would received repeated Bolous duos if needed. During spinal anesthesia, BP and HR were checked for 75 minutes (every 3 minutes for the first 15-minute period and every 10 minutes for the following 60-minute period). Also nausea and vomiting were recorded during the surgery. Acid-base status was investigated for arterial umbilical cord blood after the extraction of fetus and umbilical cord clamp. Also neonatal Apgar was checked at 1 and 5 minutes after birth.