Aldosterone is a key regulator of water and electrolyte metabolism, but recent evidence from multiple lines of research also identifies it as a major player in other chronic disorders, particularly diabetes and the metabolic syndrome.In this review, we summarize relevant aspects of aldosterone production, secretion, action, the way aldosterone and the mineralocorticoid receptor may impact energy metabolism, and useful take-home messages concerning mineralocorticoid antagonism in patients with type 2 diabetes mellitus.(Rev ALAD.