A ”manic state” which appeared periodically or episodically was observed in two cases in adolescence. The duration of this condition was short and prognosis was good. Psychiatric symptoms in one female patient were not coincident with the menstrual cycle. Both cases showed no abnormalities on EEG. Judging from symptoms and clinical course, this disease is akin to periodic psychosis, but ”self-conceit”, as a protective reaction to a critical situation against mental stress may have taken the form of a ”manic state”.