A randomized trial showed that Surgery speeds up recovery of patients suffering sciatica for 6 weeks but Prolonged conservative care yields similar results at one year. However 39%,) of this conservative care group ultimately underwent surgery after a mean period of 18.7 weeks. We evaluated variables to improve prediction of surgery in the conservatively treated cohort. Baseline data on 142 patients enroled in the conservative treatment arm of a randomized trial were analyzed to select those that could contribute to the prediction of surgery. The actual occurrence of surgery was used as dependent outcome of interest. Variables measured at baseline included neurological examination results, the visual analogue scale for pain (VAS) and the Roland disability questionnaire (RDQ). Higher pain intensity and functional limitations at baseline were associated with an increased likelihood of surgery during follow-up. Mutually adjusted Odds Ratios of 1.7 (95% CI; 1.1-2.7) per 20 mm incremental intensification of pain on the VAS score and 1.8 (95% CI; 1.2-2.9) per 3 points of deterioration of the RDQ score quantify the increasing chance of undergoing delayed Surgery. Despite maximal efforts to the contrary, surgery Could not be prevented for a considerable proportion of patients in a conservatively treated cohort. Compared to those with lower scores initially, patients with more intense leg pain or higher disability scores were at higher risk to undergo delayed surgery. The individual surgical decision process is facilitated by the use of pain and disability scales complemented by patient preferences. (C) 2008 International Association For the Study of Pain. Published by Elsevier B.V. All rights reserved.