An unusual case is reported in which a posttraumatic peudomeningomyelocele developed over many years inside the body of a fractured lumbar vertebra, eroding the pedicle and causing progressive neurological deficit. The wall of the sac was mostly formed by the scalloped bar bone, and partly by a membrane resembling the dura. The terminal part of the conus medullaris and some nerve roots of the cauda equina formed the contents and parts of the wall of the outpouching of the subarachnoid space into the vertebral body. A comparison is drawn between this lesion and formation of an "enlarging fracture" of the skull. The surgical technique used for obliteration of this pseudomeningomyelocele is described.