This chapter looks at the natural analgesic systems of the human body. It begins by discussing the endogenous opioid systems of the body and their role in controlling pain and considers how acupuncture draws upon these systems to control pain. The chapter discusses the issues of referred pain and projected or phantom pain. It explains the role of the endogenous opioid system in the control of pain and examines the role of acupuncture in pain control. The periaqueductal grey matter of the midbrain contains a high concentration of opioid receptors which, when stimulated electrically, produce profound analgesia. Morphine and morphine-like analgesic drugs exert their effect by stimulating the same receptors as do these natural opioid peptides. Acupuncture involves placing fine needles in certain defined areas of the skin in an attempt to attain analgesia in specific parts of the body.