A 57-year-old male with prostatic cancer was scheduled for a radical prostatectomy under general anesthesia combined with epidural anesthesia. An epidural catheter was introduced at the L 1-2 interspace without problem. The patient was placed in a hyperlordotic supine position with a bolster under his lower back for the seven and a half hour operation. Upon emergence from anesthesia, he complained of severe low back pain in addition to incisional pain. On the second postoperative day, the epidural catheter was removed. After residural analgesic effects had fully disappeared, he experienced muscular weakness in the left thigh and could not walk. Regional sensory loss and edema were also observed where pressure had been applied by the bolster, although spinal cord magnetic resonance imaging studies were almost normal. It took him seven weeks to walk without the support of a brace after surgery. Hyperextension of the lumbar spine could increase the pressure on the inferior vena cava which is transmitted to the intraspinal vein, and could lead to the disci intervertebrales compression and the stress on the facet joint. We believe that the primary cause of the presented symptoms was related to this position. Prolonged and/or excessive hyperlordosis during surgery should be avoided.