BACKGROUND: Lumbar supports are used in the treatment of low back pain patients to make the impairment and disability vanish or decrease. Lumbar supports are also used to prevent the onset of low back pain (primary prevention) or to prevent recurrences of a low back pain episode (secondary prevention). OBJECTIVES: The objective of this systematic review was to assess the effects of lumbar supports for prevention and treatment of non-specific low back pain. SEARCH STRATEGY: We searched the Medline, Cinahl and Current Contents databases and the Cochrane Controlled Trials Register up to September 1999, and the Embase database up to September 1998. We also screened references given in relevant reviews and identified controlled trials, and used Science Citation Index to identify additional controlled trials. SELECTION CRITERIA: Controlled clinical trials that reported on any type of lumbar supports as preventive or therapeutic intervention for non-specific low back pain were included. DATA COLLECTION AND ANALYSIS: One reviewer extracted data from the trials considering characteristics of the study population, characteristics of the interventions and the final results for each outcome measure. The reviewer compared these findings to data regarding the same characteristics of the same studies published already in other reviews. The methodological quality was independently assessed by two reviewers. Because it was not possible to perform a quantitative analysis, a qualitative meta-analysis was performed in which the strength of evidence on the effectiveness of lumbar supports was classified as being strong, moderate, limited or conflicting, and no evidence. MAIN RESULTS: Five randomized and two nonrandomized controlled preventive trials and six randomized therapeutic trials were included in our review. Overall the methodological quality of the studies included in our review was rather low. Only four of the thirteen studies scored positive on 50% or more of the the internal validity items. There was moderate evidence that for primary prevention lumbar supports are not more effective than other types of treatment or no intervention. No evidence was found on the effectiveness of lumbar supports for secondary prevention. The systematic review of therapeutic trials showed that there is limited evidence that lumbar supports are more effective than no treatment, while it is still unclear if lumbar supports are more effective than other interventions for treatment of low back pain. REVIEWER'S CONCLUSIONS: There is still a need for high quality randomised trials on the effectiveness of lumbar supports. One of the most essential issues to tackle in these future trials seems to be the realisation of an adequate compliance.