The purpose of this study is to assess the effect of melatonin on pain and amount of blood loss after cesarean delivery one hundred twenty women with singleton term pregnancy undergoing elective or emergency lower segment cesarean section under spinal anesthesia were included in this study. The patients were randomly allocated to one of three groups of 40 each to receive sublingual 3 mg melatonin or 6 mg melatonin or placebo before spinal of anesthesia . In all patients 20 IU syntocinon which dissolved in 0.5liter of lactated Ringer's solution) at the rate of 500 ml over a 15 minutes period, immediately after delivery of the neonate was infused . Time to first requirement of analgesic supplement, Hemodynamic variables,will be recorded.Patients were instructed preoperatively in the use of the verbal rating scale (VRS) from 0 to 10 (0no pain, 10maximum imaginable pain) for pain assessment. If the VRS exceeded four and the patient requested a supplement analgesic, diclofenac Na supp 100 mg was to be given for post-operative pain relief as needed . For breakthrough pain(VRS >4) if time of administration of diclofenac Na less than 8h,Pethidine 25 mg IV was given. For determination of blood loss ,change in hemoglobin levels, need for additional oxytocics and ,the volume of blood in the suction bottle was measured, blood soaked sponges. Hemoglobin values were determined both before surgery and 12 h following surgery