An intervention that can prevent low back pain (LBP) becoming chronic, may not only prevent great discomfort for patients, but also save substantial costs for the society. Psychosocial factors appear to be of importance in the transition of acute to chronic LBP. The aim of this study was to compare the cost-effectiveness of an intervention aimed at psychosocial factors to usual care in patients with (sub)acute LBP. The study design was an economic evaluation alongside a cluster-randomized controlled trial, conducted from a societal perspective with a follow-up of 1 year. Sixty general practitioners in 41 general practices recruited 314 patients with non-specific LBP of less than 12 weeks' duration. General practitioners in the minimal intervention strategy (MIS) group explored and discussed psychosocial prognostic factors. Usual care (UC) was not protocolized. Clinical outcomes were functional disability (Roland-Morris Disability Questionnaire), perceived recovery and health-related quality of life (EuroQol). Cost data consisted of direct and indirect costs and were measured by patient cost diaries and general practitioner registration forms. Complete cost data were available for 80% of the patients. Differences in clinical outcomes between both the groups were small and not statistically significant. Differences in cost data were in favor of MIS. However, the complete case analysis and the sensitivity analyses with imputed cost data were inconsistent with regard to the statistical significance of this difference in cost data. This study presents conflicting points of view regarding the cost-effectiveness of MIS. We conclude that (Dutch) general practitioners, as yet, should not replace their usual care by this new intervention. © 2007 Springer-Verlag.