The purpose of this study was to compare the outcome of anterior lumbar interbody fusion without instrumentation (uninstrumented ALIF) against that with stable anterior cage fixation using Hartshill horseshoe instrumentation (ALIF-HH) for similar severity of disc disease. Between April 1994 and June 1998 the senior author N.R.B. performed 29 instrumented ALIF procedures with a Hartshill horseshoe cage (ALIF-HH). Between 1990 and 1998, the other senior author (J.M.H.), together with another senior consultant orthopaedic surgeon, performed 27 noninstrumented ALIF procedures using corticocancellous iliac crest autograft. All the patients in both groups had single-level fusion. An independent assessor (S.M.) performed the entire review. The mean follow-up was 4.7 years (2.3-7.9 years) in the uninstrumented ALIF group and 3.0 years (2.1-4.4 years) in the ALIF-HH group. There was subsidence of graft in four patients in the uninstrumented ALIF group. It is reasonable to assume that there was no pseudarthrosis in the ALIF-HH group. This difference was statistically significant (two-sided P-value =0.0425). On subjective score assessment, there was a satisfactory outcome (score0.05). On classification by the Oswestry Index into four categories, we found no difference in outcome between the two groups: 83.3% ( n=20) had a satisfactory outcome (defined as Excellent or Better) with ALIF and 77.8% ( n=21) had a satisfactory outcome with ALIF-HH using the Oswestry Disability Index for post-operative assessment ( P>0.05). The results of this study indicate that the Hartshill horseshoe cage does improve the fusion rate, but does not affect clinical outcome.