The present study was carried out on eighteen nonmedicatedd clinically healthy donkeys. The technique for catheteriztion of the subarachnoid space at the Lumbosacral intervertebral foramen was desscribed. According to the type of the anaesthetic used, the animals were divided into three equal groups each of six donkeys. Duration and anaesthetized area were determined in each group after administrating a fixed initial and fractional dose of ketamine, bupivacaine 0.5% and a mixture of ketamine and bupivacaine in the 1st, 2nd and 3rd group respectively. It was found in the 1st group that the onset of analgesic effect strated 2-3 minutes after the end of injection. The onset of analgesic effect in the 2nd and 3rd groups was observed immediately after the end of injection. The anaesthetized area was nearly the same in all groups. The total analgesic period in 1st group was 78 minutes. In 2nd group, it was 150 minutes while in 3rd group, it was in an average of 212 minutes. Throughout this study, it could be concluded that the use of a mixture of ketamine and bupivacaine gave the longest duration of analgesia in comparison with the other two groups.