In the last years there has been an increasing interest in psychiatric surveys as basis of epidemiologic studies and morbidity investigations. Numerous statistics from hospitals, from general psychiarists and general practioners have been referred to and constitute the basis for the 'Enquete zur Lage der Psychiatrie in der Bundesrepublik Deutschland'. The out-patient-service of the Rheinische Landesklinik Köln-Merheim is operating in line with the recommendations of the Enquete committee as one of the first psychiatric establishments in the BRD and as the first in Nordrhein-Westfalen. It consists in a community psychiatric service closely attached to a psychiatric clinic, which is in charge of the overall psychiatric assistance for a municipal district of 500.000 inhabitants. The present study outlines the frequency and categories of psychiatric diagnosis in the psychiatric out-patient-service during a period of 9 months. The case register of ICD underlies the classification of mental diseases. By evaluating a rating scale which had been established for every patient it was possible to demonstrate correlations between diagnosis, age, sex, social status, marital status and nationally. Almost all diagnosis groups demonstrate a prevalence of the female sex except for alcoholism, drug addiction and gerontopsychiatric troubles. Neurotic diseases come at the first place, followed by schizophrenic illnesses. Compared to an evaluation of 1975 there has been an increase of schizophrenia. This fact reveals a modification of concept which puts more stress on after care of ancient in-patients. This group of patients will probably represent the greatest share of out-service patients in future.