This paper has 3 purposes: (1) to report an experiment which showed that severe mental stress caused a rise in serum levels of 4S and 7S class proteins; (2) to review the literature concerning the effect of mental stress and disturbances of the diencephalon and hypothalamus upon the blood proteins and the immunological mechanisms; (3) to posit that the functional psychosis is but one expression of a general metabolic disorder which is contributed to by the effects of both stress and hypothalamic-hypophyseal action. The finding of abnormal serum proteins in so-called functional psychoses was documented and extensively reviewed in previous communications.12-17It seemed likely that these abnormalities might be connected intimately with the genesis of the psychosis, since they were seen in a group of acutely mentally disturbed patients very early in the course of their illness and before they had received drug or electroshock therapy.12,14,15It