Hypertension is an important determinant of heart failure. Ventricular systolic and/or diastolic dysfunction can eventuate in an activation of the renin-angiotensin-aldosterone system (RAAS). Circulating RAAS effector hormones lead to: the appearance of the congestive heart failure syndrome; and a systemic illness that features oxi/nitrosative stress in various tissues, including blood, together with circulating pro-inflammatory cytokines, anorexia and, ultimately, cachexia. In addition to its well-known endocrine properties, expressed in epithelial cells of classic target tissues, aldosterone (ALDO) has an emerging portfolio of actions in nonclassic target tissues, such as circulating lymphocytes and monocytes (or peripheral blood mononuclear cells [PBMC]). This neuroendocrine-immune interface is based on Na(+)-dependent, ALDO-induced iterations in PBMC cytosolic free [Mg(2+)](i) and [Ca(2+)](i). Ca(2+) loading contributes to an induction of oxi/nitrosative stress and activation of PBMC transcriptome. This immunostimulatory state begets a pro-inflammatory/fibrogenic vascular phenotype involving the heart and systemic organs and can be prevented by either ALDO receptor antagonism or antioxidant. The established efficacy of ALDO receptor antagonism as an integral component of the overall management of symptomatic heart failure may include its immunomodulatory properties. This brief review traces studies that led to and then identified the neuroendocrine-immune interface that accompanies aldosteronism.