Background: Spinal anaesthesia (subarachnoid block) is the most popularly performed procedure in the field of anaesthesiology. The aim of the present study was to compare intrathecal 10 mg of 0.5% hyperbaric bupivacaine versus intrathecal 10 mg of 0.5% hyperbaric bubivaciane with 25 microgram fentanyl  versus  nalbuphine in doses 1, 5 and 10 mg with 10 mg of 0.5% hyperbaric bupivacaine in patients undergoing elective caesarean section under subarachnoid block (SAB). Methods: This study included 100 patients were divided into 5 groups randomly allocated using a sealed envelope technique each group contain 20 patients; group A (control group): intrathecal10 mg of 0.5% hyperbaric bupivacaine, group B: intrathecal10mg of 0.5% hyperbaric bupivacaine +  fentanyl 25 microgram. group is group C: intrathecal10 mg of 0.5% hyperbaric bupivacaine+  nalbuphine 1 mg. group D: intrathecal10 mg of 0.5% hyperbaric bupivacaine +  nalbuphine 5 mg. group E: intrathecal10mg of 0.5% hyperbaric bupivacaine +  nalbuphine 10 mgResults &Conclusion: Nalbuphine 0.8 mg is better than fentanyl in enhancing the period of postoperative complete and effective analgesia, diminishing the need of postoperative rescue analgesics and has better features such as anti-pruritic, lesser shivering, nausea and vomiting so nalbuphine 0.8 mg is safe, valuable and the best among the groups.