STUDY DESIGN: This prospective study examines the appropriateness of indications for surgery of herniated intervertebral disc and spinal stenosis in patients undergoing surgery in a university hospital setting. OBJECTIVE: To evaluate the appropriateness of surgery using explicit criteria developed by an expert panel in the United States. SUMMARY OF BACKGROUND DATA: The use of surgery for herniated intervertebral disc and spinal stenosis varies widely within and among countries. It has been postulated that the main reason for treatment failure is poor selection of candidates for the procedure. METHODS: The authors prospectively evaluated appropriateness of surgical indications for herniated lumbar intervertebral disc or spinal stenosis in 328 consecutive patients undergoing the operation in two university neurosurgery departments. Outcome was measured 1 year after surgery by a standardized interview. RESULTS: Indications for surgery were considered to be appropriate or equivocal in 202 (62%) patients and inappropriate in 126 (38%). Among the 126 inappropriate procedures, 66 were so rated because of insufficient activity restriction before the procedure. One year after surgery, 74% of the patients perceived the results of the operation as good or very good. CONCLUSIONS: Appropriateness as measured by the criteria established by the American panel identified a large percentage of day-to-day practice in the two surgical units as inappropriate. However, use of criteria that include new findings about lack of efficacy of bed rest probably would lower this percentage. Criteria of appropriateness of medical and surgical procedures, developed through the panel process, need to be updated regularly.