How can we study the 'quality of psychoanalytic treatments'? The authors attempt to answer this question by discussing a naturalistic, multi-perspective and representative follow-up study of psychoanalyses and long-term psychoanalytic psychotherapies. We studied a representative sample (n = 401) of all the patients who had terminated their psychoanalytic treatments with members of the German Psychoanalytical Association (DPV) between 1990 and 1993. Between 70 and 80 per cent of the patients achieved (average 6.5 years after the end of treatment) good and stable psychic changes according to the evaluations of the patients themselves, their analysts, independent psychoanalytic and non-psychoanalytic experts, and questionnaires commonly applied in psychotherapy research. The evaluation of mental health costs showed a cost reduction through fewer days of sick leave during the seven years following the end of long-term psychoanalytic treatments. The results achieved using non-psychoanalytical instruments are complemented by the richness of the idiosyncratic findings, gained by the psychoanalytic research instruments.