Depressive diseases are among the most frequent illnesses. They are only partly recognized and treated. The largest number of depressed patients are found in the offices of the general practitioner and internist. Only a small fraction of patients with severe, predominantly endogenous psychotic depressions are treated in hospital. The following consequences arise from this frequency distribution: by improvement of diagnostic methods to recognize, if at all possible, all depressed patients requiring therapy and to treat them suitably; by improvement of prevention, primary in risk groups and tertiary in prophylaxis of recurrence, to lower the morbidity of depression; and by improvement of ambulant therapy with regard to controlling suicidal tendencies and anxiety and prevention of chronicity and resistance to therapy to reduce the necessity for hospitalization.