The results for sixty-two patients who had had a diagnosis of diabetes mellitus and lumbar disc disease or spinal stenosis and had been managed with a posterior decompressive procedure were compared, in a retrospective study, with those for sixty-two age and sex-matched non-diabetic (control) patients who had had similar operative procedures. Forty-four of the sixty-two diabetic patients and fifty-five of the non-diabetic patients were available for long-term follow-up (mean, five and seven years, respectively). Among the diabetic patients, there were high rates of postoperative infection and prolonged hospitalization compared with the rates for the control group. The long-term result was excellent or good for seventeen (39 per cent) of the forty-four patients who had diabetes mellitus and for fifty-two (95 per cent) of the fifty-five non-diabetic patients. The poor results in the diabetic patients may have been related to coexisting diabetic neuropathy, to the associated microvascular disease that affects the spinal nerve roots in diabetic patients, or to the failure of the nerve roots of these patients to recover after decompressive procedures.