In this study, we have investigated the effects of intrathecal morphine injection on spinal anaesthesia components, some selected vital signs and respiratory functions. Fifty patients were evaluated. Half of the patients received morphine and lidocaine in- trathecally, and half of them received intrathecal lidocaine alone. The results revealed that intrathecal injection of morphine does not cause unwanted side- effects in the circulatory and respiratory systems.