In this paper the author offers the hypothesis that the ego possesses a function which aims at splintering the dynamic complexes of drives, object relationships, and the emotions and feelings connected with them; this he calls the fragmentizing function of the ego. Examples of this function have been observed by other writers, and under normal conditions of sleep and in the play of children. It precedes and accompanies all the known defense mechanisms and is a precondition that makes them possible. The relevant portion of the transference neurosis of a masochistic patient is ably discussed in support of this hypothesis.