Every serious school of psychotherapy has its own theory-often only vaguely formulated-concerning the active ingredients in psychotherapy. Many of these theories are presented as mutually exclusive. The author presents an overview of some of the important, primarily psychoanalytically founded, theories of the factors in individual psychotherapy that are responsible for inducing change. It is impossible to pinpoint any single factor that is crucial in every therapy. What is needed is a nondogmatic, multiple-factor model that successfully incorporates the knowledge obtained from the many existing theories of psychotherapyinduced change. In practice, it is often difficult to maintain the traditional distinction between specific and nonspecific factors, just as it is difficult to distinguish the roles played by purely therapeutic factors-relating to the technique of the therapist-and by extratherapeutic factors. The author also addresses the epistemological status of the various claims put forward, by the many different theories of psychotherapy, concerning the active ingredients in psychotherapy.Today it is generally accepted that psychotherapy works for most forms of psychopathology. However, there is still considerable disagreement as to what makes psychotherapy effective: What are the active ingredients in psychotherapy, or what factors in the therapy are responsible for effecting change? In his classic contribution to the understanding of the therapeutic elements in psychotherapy, Jerome Frank (1971;Frank & Frank, 1991) lists four general factors that are essential, in his view, to every form of psychotherapy: (a) a particular kind of emotionally charged relationship between the patient and the therapist that supports the patient's confidence in the therapist's competence and in his desire to help; (b) the fact that psychotherapy and its institutional context are socially sanctioned and legitimized, which in itself enhances the patient's expectations of help; (c) the immanent rationale or myth behind any given therapy, which offers an explanation of the