Objectives: Comparison the effect of intrathecal meperidine and fentanil added to bupivacaine 0.5% for elective Cesarean section. Study Design: a randomized, double-blind, clinical trial. Inclusion criteria: pregnant women, ASA I-II with singleton pregnancies who were underwent elective Caesarean section, Exclusion criteria: Patients with cardiovascular disorders, renal failure, coagulopathy, sensitivity to the drugs, preeclampsia, lack of consent and spinal anesthesia contraindication, history of seizures or other neurological diseases, (IUGR). 120 Patients were randomly divided into 3 groups: Group1 : bupivacaine 0.5% (8mg), 15 micrograms fentanil and 0.1 ml normal saline total volume 2ml.Group2 : bupivacaine 0.5% (8mg), 15 mg of meperidine and 0.1 ml normal saline total volume 2ml. Group3: bupivacaine 0.5% (10 mg) (total volume 2 ml. Measured variables: Time of onset: the time interval intrathecal injection and loss of sensation in the T10, The maximum level of sensory block and time to reach to the maximum level of sensory block, the level of sensory block after 120 min, the duration of sensory block, Onset of motor block, duration of motor block, the maximum level of motor block, shivering, pruritus, nausea, vomiting were checked during and after operation every 10 min in the recovery room every 10 min, Hypertension, bradycardia, time of discharge from recovery room, Apgar score at 1 and 5 minutes.