Acupuncture ... is based on the traditional Chinese theory of meridian-energy pathways that are believed to run through the body, carrying the vital force or energy called chi. In this therapy, the flow of chi is controlled by the insertion of hair-thin needles at specific points... [and] must be performed by a trained practitioner.

An average treatment involves the insertion of 5 to 15 fine needles. They may penetrate as little as a fraction of an inch or as much as three or four inches (where a thick layer of fat or muscle exists). The procedure usually causes little pain, although often there may be a tingling or a heavy sensation.

The ability of acupuncture to relieve pain in many patients is well documented, and the physical basis of the pain relief has been demonstrated through laboratory tests on animals; acupuncture releases endorphins and other forms of neuro-transmitters that serve as the body's natural painkillers. However, researchers remain unclear as to how acupuncture is able to provide long-lasting pain relief... Acupuncture has [also] been found effective in stroke rehabilitation, relieving nausea...[and] has been recommended as a treatment for drug addiction.