The term trapezoid nucleus refers to one of four components of the superior olivary complex as classically defined by Nissl stain in the human. It is located ventrally in the pontine tegmentum. The other components of the complex are the superior olive and the periolivary region ( Carpenter-1983 ). Some authors describe it as indistinctly divisible into a medial trapezoid nucleus and lateral trapezoid nucleus ( Crosby-1962 ). More recent studies based on multiple stains for calcium binding proteins failed to demonstrate a distinct group of cells identifiable as the trapezoid nucleus in the human ( Bazwinsky-2003 ). Embedded in the dorsal portion of the trapezoid body ventral to the pontine reticular formation and lateral to the medial lemniscus of the pons, it is found in the macaque ( Bazwinsky-2005; Paxinos-2009a ), the rat ( Paxinos-2009b ), and the mouse ( Franklin-2008 ). Functionally the trapezoid nucleus is part of the subcortical auditory system ( Swanson-2004 ).