STUDY DESIGN. An economic evaluation alongside a randomized clinical trial in primary care. A total of 135 patients were randomly allocated to physical therapy added to general practitioners' care (n = 67) or to general practitioners' care alone (n = 68). OBJECTIVE. To evaluate the cost-effectiveness of physical therapy and general practitioner care for patients with an acute lumbosacral radicular syndrome (LRS, also called sciatica) compared with general practitioner care only. SUMMARY OF BACKGROUND DATA. There is a lack of knowledge concerning the cost-effectiveness of physical therapy in patients with sciatica. METHODS. The clinical outcomes were global perceived effect and quality of life. The direct and indirect costs were measured by means of questionnaires. The follow-up period was 1 year. The Incremental Cost-effectiveness Ratio (ICER) between both study arms was constructed. Confidence intervals for the ICER were calculated using Fieller's method and using bootstrapping. RESULTS. There was a significant difference on perceived recovery at 1-year follow-up in favor of the physical therapy group. The additional physical therapy did not have an incremental effect on quality of life. At 1-year follow-up, the ICER for the total costs was €6224 (95% confidence interval, -10419, 27551) per improved patient gained. For direct costs only, the ICER was €837 (95% confidence interval, -731, 3186). CONCLUSION. The treatment of patients with LRS with physical therapy and general practitioners'care is not more cost-effective than general practitioners'care alone.