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=0.5 years, 0.5-2 years, 2-5 years, >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<or=0.02). The results after 3 months are: Verum+COT 77% (95%ci 62-88%), Sham+COT 29% (95%ci 16-46%), nil+Cot 14% (95%ci 4-30%) - effects are significant for Verum+COT over Sham+COT (P<or=0.001) and for Verum+COT over nil+COT (P<0.001). No difference was found in the mobility of the patients nor in the intake of NSAID diclofenac. Our conclusion is that acupuncture can be an important supplement of conservative orthopedic treatment in the management of chronic LBP.