The neuroendocrine system and the immune system have been shown to be mutually interacting at different levels. In the present report we focus on the mechanism(s) by which the activity of the immune system can be influenced by the neuroendocrine system. In the first part we describe some major pathways involved in neuroendocrine-immune interactions at the level of functional effects as well as cell biological mechanisms involved. Evidence is summarized showing that the ultimate effect of a myriad of hormones and neurotransmitters will determine the ultimate outcome of the immune response. In the second part we describe the regulation of the secretion of the neuropeptide beta-endorphin by cells of the immune system.