The cauda equina syndrome is a relatively uncommon, but serious complication. And it can have grave long-term consequences for the patient. The purpose of the study is to analyse the causes, clinical courses and to find the methods of prevention of cauda equina syndrome following lumbar spine surgery. We reviewed 6 cases among 287 patients wbo had been operated on and followed for minimum 12 months at Seoul Adventist Hospital from March 1991 to March 1996. The obtained results were as follows. 1. All six cases was noted only in patients who had operative procedures for spinal stenosis and possible causes were 3 cases of epidural hamatoma, 1 case of unrecognized and recurred disc herniation, 1 case of retained ligament flavum and 1 case of pseudomeningocele formation due to unrecognized dura tear. 2. Progressive neurologic deficits, decreased perianal sensation and loss of anal wink were present in all cases and were diagnostic. 3. Only three cases which were occurred within 24 hours and early treated within 12 hours, had no specific residual neurologic deficits. In conclusion, it is recommended that operators should be very cautious during the spine surgery. And also early recognition and surgical decompression is very important. During early postoperative periods, only repeated and regular neurologic examinations will enable early diagnosis and treatment to reduce permanent neurological damage.