The paper describes the application of the system of "operationalized psychodynamic diagnosis" (OPD) which was developed in a multicentric effort during the recent years. The system is used for the classification of videotape-recorded interviews with 30 patients prior to inpatient psychotherapy. The classification system allows the diagnostic assessment of the patients' illness behaviour, their interpersonal relationships, their conflicts, psychic structure and their symptoms. The aim of the study was a description of the patient group as well as a test of the relationship between diagnostic features and treatment outcome following several months of inpatient group psychotherapy. The study confirms the practicability of the OPD-system and shows that the description of the patient group seems to be plausible and valid. Single diagnostic categories seem to be useful for the prognosis of treatment outcome, especially structural features, but also characteristics of the patients' illness behaviour and their sensitivity for conflicts.