Of all Freud's writings, Bion was most deeply influenced by “Formulations on the Two Principles of Mental Functioning” (1911), and the author asserts that much of Bion's major theoretical thinking may be seen as an elaboration of this paper. Bion's introduction of the concept of alpha function, which “may be regarded as a structure” (Bion 1962, p. 26), constitutes what the author calls “Bion's ego psychology.” A clinical implication of Bion's ego psychology is a focus upon the unconscious interaction between the analyst's and the patient's communicating alpha functions. Clinical material from the analysis of an adolescent is offered to illustrate the author's points.