By means of a psychiatric case register the total psychiatric population in the Nacka region (75,000 inhabitants) was analysed during a 2-year period with regard to the amount of psychotherapy consumed in different social groups. Among the patients, the utilization of psychotherapy was 60% for social group I compared with 30% for social group III. However, the lowest social groups are overrepresented at the mental health unit. Thus, among the total population, the utilization of psychotherapy was 1.8% for social group I compared with 5.3% for social group III. The study discusses the "clinical fallacy", by which data from a patient population is applied to the whole population, giving wrong or restricted perspectives to the problem studied. It is claimed that the selectivity of the psychiatric organization concerning social groups is an important factor for the so-called "social class bias" in psychotherapy.