Pain and nausea and vomiting are of serious complications following the use of opiates after surgery, especially cesarean section. Control of postoperative complications is one of the necessities of quality promotion of health-care system. Medications with few side effects such as corticosteroids including dexamethasone can be an appropriate option. In addition, the route of administration can have a significant effect on the effectiveness of the drug. The aim of the present study was to compare the effects of intrathecal with intravenous dexamethasone in reducing the complications associated with intrathecal morphine after cesarean section.