The term “referred pain” is used for pain localized not in the site of its origin but in areas that may be adjacent or at a distance from such a site, generally comprised in the same metameres. Pain can be referred by deep somatic or by visceral structures. Myofascial pain syndrome is a typical syndrome characterized by referred pain from deep somatic structures. Referred pain from visceral organs is the most important from a clinical point of view. The patterns of referred pain orginating from various viscera are important for a correct diagnosis. Different pathogenetic mechanisms may be involved in the onset of referred pain: convergence of impulses in the central nervous system and reflexes inducing muscle contraction, sympathetic activation, and antidromic activation of afferent fibers, which induces socalled “neurogenic inflammation”.