Teitelbaum, Hall, and Phillips study and report four cases of multiple sclerosis on the basis of the holistic concept of personality as an organismenvironment system. In this as well as in other organic diseases of the nervous system, the authors feel that a physiological cortical disintegration takes place with subsequent reintegration at a lower level of functioning, and that this is the physiological aspect of the same mechanism which in psychoanalytic terms is the psychological phenomenon of regression. The premorbid personality determines the extent to which this occurs and the degree of resistance against it.