To test whether patients with persistent non-specific low back pain, when offered access to traditional acupuncture care alongside conventional primary care, gained more long-term relief from pain than those offered conventional care only, for equal or less cost. Safety and acceptability of acupuncture care to patients, and the heterogeneity of outcomes were also tested. A pragmatic, two parallel group, randomised controlled trial. Patients in the experimental arm were offered the option of referral to the acupuncture service comprising six acupuncturists. The control group received usual care from their general practitioner (GP). Eligible patients were randomised in a ratio of 2:1 to the offer of acupuncture to allow between-acupuncturist effects to be tested. Three non-NHS acupuncture clinics, with referrals from 39 GPs working in 16 practices in York, UK. Patients aged 18-65 years with non-specific low back pain of 4-52 weeks' duration, assessed as suitable for primary care management by their general practitioner. The trial protocol allowed up to ten individualised acupuncture treatments per patient. The acupuncturist determined the content and the number of treatments according to patient need. The Short Form 36 (SF-36) Bodily Pain dimension (range 0-100 points), assessed at baseline, and 3, 12 and 24 months. The study was powered to detect a 10-point difference between groups at 12 months post-randomisation. Cost--utility analysis was conducted at 24 months using the EuroQoL 5 Dimensions (EQ-5D) and a preference-based single index measure derived from the SF-36 (SF-6D). Secondary outcomes included the McGill Present Pain Index (PPI), Oswestry Pain Disability Index (ODI), all other SF-36 dimensions, medication use, pain-free months in the past year, worry about back pain, satisfaction with care received, and safety and acceptability of acupuncture care. A total of 159 patients were in the 'acupuncture offer' arm and 80 in the 'usual care' arm. All 159 patients randomised to the offer of acupuncture care chose to receive acupuncture treatment, and received an average of eight acupuncture treatments within the trial. Analysis of covariance, adjusting for baseline score, found an intervention effect of 5.6 points on the SF-36 Pain dimension [95% confidence interval (CI) -1.3 to 12.5] in favour of the acupuncture group at 12 months, and 8 points (95% CI 0.7 to 15.3) at 24 months. No evidence of heterogeneity of effect was found for the different acupuncturists. Patients receiving acupuncture care did not report any serious or life-threatening events. No significant treatment effect was found for any of the SF-36 dimensions other than Pain, or for the PPI or the ODI. Patients receiving acupuncture care reported a significantly greater reduction in worry about their back pain at 12 and 24 months compared with the usual care group. At 24 months, the acupuncture care group was significantly more likely to report 12 months pain free and less likely to report the use of medication for pain relief. The acupuncture service was found to be cost-effective at 24 months; the estimated cost per quality-adjusted (QALY) was 4241 pounds sterling (95% CI 191 pounds sterling to 28,026 pounds sterling) using the SF-6D scoring algorithm based on responses to the SF-36, and 3598 pounds sterling (95% CI 189 pounds sterling to 22,035 pounds sterling) using the EQ-5D health status instrument. The NHS costs were greater in the acupuncture care group than in the usual care group. However, the additional resource use was less than the costs of the acupuncture treatment itself, suggesting that some usual care resource use was offset. Traditional acupuncture care delivered in a primary care setting was safe and acceptable to patients with non-specific low back pain. Acupuncture care and usual care were both associated with clinically significant improvement at 12- and 24-month follow-up. Acupuncture care was significantly more effective in reducing bodily pain than usual care at 24-month follow-up. No benefits relating to function or disability were identified. GP referral to a service providing traditional acupuncture care offers a cost-effective intervention for reducing low back pain over a 2-year period. Further research is needed to examine many aspects of this treatment including its impact compared with other possible short-term packages of care (such as massage, chiropractic or physiotherapy), various aspects of cost-effectiveness, value to patients and implementation protocols.