In 19 patients with meningiomas of the olfactory fossa the author established a certain development of the psychopathological symptomatology. First of all asthenia ensues, eventually a complacent mood with an underestimation of the severity of the disease and an emotional crudeness is seen. These disorders are gradually substituted by euphoric dementia with a tendency towards foolish jokes, anosognosia of the disease, severe intellectual disorders and a desintegration of the "personality nuclei" with desinhibited drives. The intellectual disorders are expressed not in formal disturbances (logic operations), but in insufficient goal-directness and uncritical thinking.