In 1896 Kraepelin described（involutional）melancholia as a single clinical entity separate from manic-depressive psychosis. Because of the high incidence of depression in the involutional period, its symptomatic characteristics, and somewhat poor prognosis, this was recognized as valid at that time. Nowadays,the broadening concept of mood disorder denies involutional melancholia as a valid independent entity,and so it is included in mood disorders. A closer psychopathological inspection, however, still reveals several crucial differentiating points,which suggest that should be separated from the current mood disorder concept. Its cardinal symptoms are as follows : unveiled basic anxiety（Schneider K）, specific autistic thinking（Kranz H）,lack of insight,dissimulation,and severe suicidal thoughts. Patients fear that their innermost mind will be revealed, try to hide it, and even pretend to be healthy. Melancholic patients are believed to be at an extremely high risk of suicide. Difference between species and types of disease and the diagnostic hierarchial rule,which classifies all mental disorders into four different hierarchies（groups）, are also referred to. The reevaluation of involutional melancholia is imperative for the present field of clinical psychiatry.