In recent years the relationships among immune, endocrine and nervous systems have been extensively studied, and grouped in a new research field: psychoneuro-immunoendocrinology. Since ancient times its has been known that, in humans, mood as well as environmental influences could affect health. In the late '70s, only, evidence of bi-directional pathways has been achieved, first in animal models and, later on, in humans. We reviewed current knowledge on neuroimmunomodulation, concerning the influence of stress and psychological status on immunity as well as neuroendocrine modulation by the immune system, reporting some data obtained from our studies. Particularly, having detected a relevant impairment concerning most of the parameters studied, we emphasized the effects of depressive disorders on immune function in the elderly.