The capability of reflex points on the external ear to alter neuromuscular and neuropathic disorders has been attributed to the descending pain inhibitory pathways of the central nervous system. The inverted fetus perspective of the somatotopic arrangement of auricular acupuncture points was first described in the 1950's by Dr. Paul Nogier of France, and has received scientific support from double blind studies examining auricular diagnosis of musculoskeletal and of coronary disorders. Acupuncture points on the ear and on the body have lower levels of electrical skin resistance than surrounding tissue. These electrodermal differences are apparently related to autonomic control of blood vessels rather than increased sweat gland activity. The heightened tenderness of reactive acupuncture points may be explained by the accumulation of noxious, subdermal substances. Electrical stimulation of specific points on the external ear leads to site specific neural responses in different regions of the brain. Behavioral analgesia produced by auricular acupuncture can be blocked by the opiate antagonist naloxone, indicating the role of endorphinergic systems in understanding the underlying mechanisms of auriculotherapy. The anatomical structures and electrical application of the auricle are described as they relate to the localization of master points, musculoskeletal points, internal organ points, and neuroendocrine points.