Diagnostic external fixation was performed in 101 patients with disabling low back pain. In 47 patients, pain was relieved by stabilization but returned after destabilization. These patients were considered good candidates for a fusion operation. Results after fusion are available for 34 patients: 14 (41%) patients had a good, 12 (35%) had a fair, and 8 (14%) had a bad result. In two patients, pain was relieved by stabilization and did not return after fixator removal; no fusion operation was performed. Fifty-two patients did not respond positively to external fixation. Nine were operated on despite negative results with fixation. Of these, seven patients had a bad result, one a good result (however, this patient had spinal stenosis and the indication for external fixation was wrong), and, in one, the follow-up time is too short. Positive results with external skeletal fixation may predict a successful fusion operation with reasonable accuracy. If stabilization does not relieve the patient's pain, spinal fusion is unlikely to be of any benefit.