A 44 year old man complained of a left flank pain. The epidural block was performed. After two hours he suddenly experienced severe back pain, lower limb numbness and weakness of the legs. The physical examination revealed the flaccid paraplegia and the disturbance of pain and touch sensation. But his proprioceptive sensation was preserved. The paraplegia gradually disappeared and he had no neurological deficit. Judging from the unique sensory disturbance, the anterior spinal artery syndrome was suspected.