This prospective, randomised controlled trial, with three parallel groups, patient and observer blinded for verum and sham acupuncture and a follow up of 3 months raises the question: "Does a combination of acupuncture and conservative orthopedic treatment improve conservative orthopedic treatment in chronic low back pain (LBP). 186 in-patients of a LBP rehabilitation center with a history of LBP >or=6 weeks, VAS >or=50mm, and no pending compensation claims, were selected; for the three random group 4 weeks of treatment was applied. 174 patients met the protocol criteria and reported after treatment, 124 reported after 3 months follow up. Patients were assorted 4 strata: chronic LBP, or=5 years. Analysis was by intention to treat. Group 1 (Verum+COT) received 12 treatments of verum acupuncture and conservative orthopedic treatment (COT). Group 2 (Sham+COT) received 12 treatments of non-specific needling and COT. Group 3 (nil+COT) received COT alone. Verum- and Sham acupuncture were blinded against patient and examiner. The primary endpoints were pain reduction >or=50% on VAS 3 months after the end of the treatment protocol. Secondary endpoints were pain reduction >or=50% on VAS and treatment efficacy on a four-point box scale directly after the end of the treatment protocol and treatment efficacy after 3 months. In the whole sample a pain relief of >or=50% on VAS was reported directly after the end of treatment protocol: Verum+COT 65% (95%CI 51-77%), Sham+COT 34% (95%ci 22-49%), nil+COT 43% (95%ci 29-58%) - results are significant for Verum+COT over Sham+COT (P