The surgical experience of 120 patients with lumbosacral lipomas is described. 47 of 120 patients were preoperatively found to be neurologically intact, the remaining 73 patients presented with various neurological signs including reflex changes, sensory disturbances, muscle weakness and sphincter problems. Neuro-imagings allowed a classification of lumbosacral lipomas into five types: (1) dorsal type; (2) caudal type; (3) combined type; (4) filar type; and (5) lipomyelomeningocele. Although all 120 patients underwent untethering of the spinal cord, the nerve roots passing through the lipoma itself and the neural tissues protruding externally to the spinal canal, respectively, tended to prevent satisfactory surgical removal of the lipoma in combined type lipomas and lipomyelomeningoceles. During 8.96 years of a mean postoperative follow-up period, there was no significant deterioration in most of the patients and some patients even improved in function. However, two patients with combined type lipomas developed neurological deterioration just after surgery, and five (two dorsal, two caudal and one combined type lipomas) did in the fashion of a late-onset. There are two different patient groups of lumbosacral lipomas; one group (caudal and filar type lipomas, and most of dorsal type lipomas) in whom the surgical anatomy is simple and satisfactory untethering surgery could be done without risk, and another (combined type lipomas and lipomyelomeningocele) in whom surgery would be accompanied with some risk and sometimes complete untethering could not be achieved because of the complicated anatomy of the lesion. Surgical difficulty of the latter group can be correlated with the increased frequency of neurological deterioration occurring just after the operation, but not of delayed one. Concerning prophylactic surgery for asymptomatic patients, the former group of patients are obviously good candidates, but the latter group is not.