According to the World Health Organization (WHO), a broad definition of acupuncture is the stimulation of certain points on the body (acupuncture points) using needling, moxibustion, electricity, laser or acupressure for therapeutic purposes. The standard acupuncture nomenclature published by the WHO listed about 400 acupuncture points and 20 meridians connecting most of the points. Results from randomized controlled trials (RCTs) have shown that acupuncture is effective in treating dozens of disorders such as osteoarthritis, pelvic and back pain, neck pain , migraine and tension headache, nausea/vomiting and inflammatory bowel disease. Mixed results widely exist in acupuncture research for various reasons such as poor trial design, irregularity of this highly operator-dependent technique and the unique biological basis of acupuncture which will be explained later in this article. Many neurohumoral mechanical and growth control effects of acupuncture have been observed. Several models of acupuncture mechanism have been proposed. The focus of this article is on the biological models of acupuncture which have been prospectively tested and independently confirmed.