By means of morphological studies, it has been shown that most APs are located on or adjacent to peripheral nerve trunks or branches, capillary vessels, blood vessels, lymphatic vessels, nerve receptors, nerve endings, and mast cells. The meridians correspond to trajectories of relevant deep peripheral nerves including blood vessels [, ]. Early studies identified that myelinated and unmyelinated fibers are stimulated during acupuncture by recording the compound action potential . The acupuncture-signal transmission to the central nervous system occurred through such afferent fibers . Even the sensation that occurs during positioning of an acupuncture needle during treatment (“De qi sensation”), it is now generally accepted that it involves a multitude of fiber types, ranging from fast-conducting myelinated Aβ fibers of high threshold to slow-conducting unmyelinated C fibers with relatively low thresholds [, ]. In addition, lesion of nerves, block of neuronal activity, reduction of neurotransmitter release (by pharmacologic intervention), or by lesioning the spinal cord or supraspinal regions, prevents the action of acupuncture on the function of the following systems: cardiovascular function [, ], nociceptive or nonnociceptive pathways [, ], immune responses [, ], digestive system [, ], and neuroendocrine regulation [, ]. Therefore, the nerves within these meridians and acupoints are probably involved in the therapeutic effects of acupuncture (Figure 1).