Until recently, vitrually all interactions between the pituitary-adrenocortical axis and the immune system were largely attributed to the effects of glucocorticoids. Research in the last few years however has led to a drastically altered view of this interaction. This has principally resulted from the observations that cells of the immune system have receptors for, and are directly affected by, pituitary and hypothalamic peptides. Further, pituitary peptide hormones seem to be endogenous to the immune system and may act in an autocrine as well as endocrine fashion. As a result of these new developments, as well as a number of recent reviews on the effects of glucocorticoids om immune function this chapter will focus on the more recent findings.