Fifty-one patients having lumbar or lumbosacral posterolateral fusion with pedicle screw internal fixation were reviewed retrospectively two years after the fusion by an independent observer. In 44 patients, the underlying condition was lytic or degenerative spondylolisthesis. The internal device was removed one year after the fusion. The fusion rate was 94%. The subjective disability was assessed using the Oswestry disability index. The mean Oswestry score was 38% preoperatively, and 24% two years after the fusion. Preoperatively, only every fifth patient was able to work; two years postoperatively, almost 60% held jobs. Complications due to internal fixation were recorded in 57% of the cases. Most of these, such as screw breakage and screw loosening in the sacrum, were of no clinical importance. The use of internal fixation seems to enhance the fusion rate but is associated with more complications than posterolateral fusion without implants.