The authors outline a classification of identification based on the major functions it serves in psychic structure. Identification is important in ego formation; it serves as a defense against id impulses, superego pressures, and the external world as a part of denial; further it may serve the ego in the resolution of intrasystemic conflicts. Identification may work in the service of the id (e.g., preservation of the object) or in deference to the superego. In the service of the id or superego it may seriously impair total ego functioning, although in some cases transient identification can be of value to the ego in reaching a satisfactory solution of psychic problems. More often than not it is necessary to know the functions of a patient's major identifications in order to understand his lifelong neurotic problems. Illustrative clinical material is presented.