Chronic fatigue is investigated and analyzed as a danger signal which functions as a psychoneurotic symptom. The biological function of the feeling is that of a danger signal which protects the organism from injury through too great activity of any part of the body. In some diseases it acts as a signal to avoid all activity which might impair the reparative mechanisms of the body. In relation to the social environment it operates to warn of the danger which threatens the social self, the individual's concept of himself in relation to his fellows and to the ideal image of himself embodied in his conscience. An awareness of ego impoverishment is the basic psychological fact expressed in the feeling of fatigue.