The paper presents contemporary research on the effectiveness of psychotherapy. It deals briefly with the historical context of research of the effect of psychotherapy and the contemporary trend of empirical evidence of the effectiveness of psychotherapy. It also presents the tools for measuring the effectiveness or psychotherapy. Special attention is devoted to the methodology of randomized controlled clinical trials. It presents also alternatives of experimental clinical tests such as: natural research into the therapeutic effect, satisfaction of patients with psychotherapy, experimental case-records, qualitative investigation of the effect, qualitative evaluation of case-records. The paper deals also briefly with the so-called dosage effect of psychotherapy. It presents also the type of research which investigates the influence of variables on the part of the therapist and client which influence the effect of psychotherapy.

        Key words: psychotherapy, research in psychotherapy, research into the effect of psychotherapy, methodology.