BACKGROUND Chronic low-back pain (LBP) affects a significant proportion of the population. Transcutaneous electrical nerve stimulation (TENS) was introduced more than 30 years ago as an adjunct to the pharmacological management of pain. However, despite its widespread use, the usefulness of TENS in chronic LBP is still controversial. OBJECTIVE The aim of this systematic review was to determine the effectiveness of TENS in the management of chronic LBP. METHODS We searched the Cochrane Central Register of Controlled Trials (Issue 2, 2005), MEDLINE, EMBASE and PEDro up to April 1, 2005. METHODS Only randomized controlled clinical trials (RCTs) evaluating the effect of TENS on chronic LBP were included. Abstracts were excluded unless further data could be obtained from the authors. METHODS Two reviewers independently selected trials and extracted data using predetermined forms. Heterogeneity was tested with Cochrane's Q test. A fixed effect model was used throughout for calculating continuous variables, except where heterogeneity existed, in which case, a random effects model was used. Results are presented as weighted mean differences (WMD) with 95% confidence intervals (95% CI), where the difference between the treated and control groups was weighted by the inverse of the variance. Standardized mean differences (SMD) were calculated by dividing the difference between the treated and control by the baseline variance. SMD were used when different scales were used to measure the same concept. Dichotomous outcomes were analyzed with odds ratios. RESULTS The only two RCTs (175 patients) meeting eligibility criteria differed in study design, methodological quality, inclusion and exclusion criteria, type and method of TENS application, treatment schedule, co-interventions and final outcomes. In one RCT, TENS produced significantly greater pain relief than the placebo control. However, in the other RCT, no statistically significant differences between treatment and control groups were shown for multiple outcome measures. Pre-planned subgroup analyses, intended to examine the impact of different stimulation parameters, sites of TENS application, treatment durations and baseline patient characteristics were not possible due to the small number of included trials. CONCLUSIONS There is inconsistent evidence to support the use of TENS as a single treatment in the management of chronic LBP. Larger, multi-center, randomized controlled trials are needed to better assess the true effectiveness of TENS. Special attention should be given to the risks and benefits of long-term use, which more appropriately addresses the realities of managing chronic low-back pain.