Eighty-five patients with degenerative lumbar spine disease and radiologic evidence of instability, all older than 50 years (mean age 63.4 years), underwent transpedicular lumbar CD-spondylodesis and posterolateral fusion between 1987 and 1992; 30 of them (mean age 60.8 years) had posterior lumbar interbody fusion (PLIF) additionally. The patients were followed up for a mean period of 32 months. Of these patients, 86% improved with respect to their pain symptoms, but only 46% showed a good to excellent overall result. Patients with fair and poor outcomes had had significantly more operations on the lumbar spine (P < 0.001), had a greater extent of preoperative lumbar kyphosis (P < 0.05), had a larger preoperative motor weakness (P < 0.05), and had less vertebral slips (P < 0.01) than patients with good to excellent outcomes. Patients treated with transpedicular spondylodesis plus PLIF did not make any better progress than those with transpedicular fusion alone. By the 6-month follow-up a significant difference in the clinical outcome was already apparent (P < 0.001), making an improvement of a then fair or poor result unlikely.