[Formulating a diagnosis in psychiatry]. 
Referring to some critical comments on operational diagnostics in view of the adoption of the 10th Revision of the International Classification of Diseases, the relevance of symptomatology for diagnosis using ICD-8 and ICD-9 was investigated in a retrospective study.  Inpatients with neurotic depression, endogenous depression, schizoaffective psychosis, manic psychosis and paranoid schizophrenia were included in the study.  Data came from routine documentation of every episode of treatment, symptoms being assessed according to the AMP system.  Discriminant analyses revealed psychopathology at admission to be the most important information for diagnosis both at admission and at discharge.  Psychopathology at discharge seemed to be of no importance for diagnosis, whereas inclusion of the reasons for referral improved discrimination between categories of depressive disorder.  When in addition sex, age, and chronicity were included in computation of the discriminant function, a further improvement in the prediction of psychiatric diagnosis at discharge resulted.  These findings are compared to others reported in the literature.