The variety of psychological and emotional responses during the treatment process are described and conceptualized as related to the structure of the therapeutic situation, the therapeutic relationship, the mobilization of conflict, the experience of affects and drive derivatives, the phenomenon of reinforcement, and the working through of the termination phase. The distinction between "core" and "derivative" psychic functions is developed, permitting a conceptual understanding of how this form of psychotherapy can produce significant and lasting intrapsychic change. Some of the differences between psychoanalytic psychotherapy and psychoanalysis are described. The general concepts are illustrated by clinical vignettes from a case of successful psychotherapy.