473 patients (261 at the long-term follow-up) with chronic low back pain had been randomly allocated to receive either surgical intervention (i.e. spinal fusion) or conservative treatment in three previous randomized controlled trials. The purpose of this study was to compare these two treatment approaches with respect to combined clinical outcomes at a mean follow-up of 11 years. Results indicated that disability on the Oswestry Disability Index (ODI) was similar between groups. When secondary outcomes were subject to an intention-to-treat analysis, no significant differences were observed in any outcome. Similar findings were observed when these outcomes were subject to an as-treated analysis, except for current back status and the proportion of patients with an ODI of 22 or less, for which spinal fusion was superior. These statistical differences, however, were not found to be clinically relevant.