Wu-t'ou is one of the terms coined by the Yuan drama theorist Chou Te-ch'ing (1277-1356) in "The Ten Methods for Composing Ch'u" of his Chung-yuan yin-yun. As Chou failed to give a precise definition, the term has given rise to quite a few different interpretations by ch'u theorists since the Ming and Ch'ing dynasties, and turned out to be one of the most controversial terms in the history of Chinese drama criticism. It is originally an aesthetic method for the creation of north ch'u. That is, the creator must take care of the literariness, versification and musicality when composing ch'u. The essay is divided into two sections. Section I, "An investigation into Chou Te-ch'ing's Theory of Wu-t'ou," analyzes three types of wu-t'ou in the commentaries of the forty san-ch'u which Chou selected. Type one, "a certain particular character as wu-t'ou," refers to an expression consisting of one character, two or three, i.e. "the eye of a poem". Type two, "a certain sentence as wu-t'ou," indicates a particularly prominent sentence in a ch'u. Type three, " a certain melody as wu-t'ou," designates a set or sets of ch'u. Section II, "The Transference and Derivatives of the Theory of Wu-t'ou in the Ming and Ching," attempts to discuss chronologically one by one the point advanced by each of the theorists. Besides comparing the differences and similarities between their theories and Chou's, it also tries to see how each of them expands the original definition of wu-t'ou. The essay explores the implications of the term, "wu-t'ou," first coined by Chou Te-ching. It not only compares the points made by every theorist, but traces its expansion and evolution. The purpose is to clarify the complications of the term in the history of Chinese drama criticism.