OBJECTIVES: To evaluate the efficacy of transcutaneous electrical neurostimulation (TENS) in patients with chronic low back pain (LBP). DESIGN: Prospective, randomized, multicentre, single-blind study. SETTING: Twenty-one French pain centres. PARTICIPANTS: Two hundred thirty-six consecutive adult patients consulting for chronic LBP, with or without radicular pain (mean age ± standard deviation: 53 ± 13 years; range: 28-86 years). INTERVENTION: Patients were randomly assigned to receive either active (n = 117) or sham (n = 119) TENS in four 1-h daily treatment sessions for 3 months. MAIN OUTCOME MEASURES: The primary outcome measured was improvement of functional status at 6 weeks (Roland-Morris Disability Questionnaire). Secondary outcome measures were improvement of functional status at 3 months, pain relief (weekly visual analogue scale assessments), positive functional repercussions of pain levels on quality of life, a diminution of the use of analgesic and anti-inflammatory medication, satisfaction with the overall treatment strategy and compliance. RESULTS: Functional status did not differ between the groups, whether at 6 weeks or 3 months (p = 0.351 at 6 weeks). A significant improvement between the first and last visual analogue scale assessments was observed in patients with either lumbar pain alone or lumbar and radicular pain treated with active TENS. Other outcome measures did not differ significantly between the two groups. CONCLUSION: There was no functional benefit of TENS in the treatment of patients with chronic LBP.