The purpose of this article is to discuss basic aspects of the interplay between the neuroendocrine and the immune systems. Two pathways link the brain and the immune system: the autonomic nervous system and the neuroendocrine outflow via the pituitary. Most of the influence of the brain on immune events is exerted through the hypothalamic-pituitary-adrenal (HPA) axis. Moreover, certain neurotransmitters, neuropeptides, and neurohormones affect immune function both in vivo and in vitro. Receptors for these molecules are present on immune cells. This cell-to-cell communication is bi-directional, since impulses from the immune system can affect many functions of the central nervous system. Cytokines released during the activation of the immune system, in turn, can alter the function of the HPA axis. In this context, we also describe our main findings working with a model of Candida albicans infection in rats exposed to chronic varied stress.