Diabetes mellitus is a major risk factor for microvascular and macrovascular disease. Many of the deleterious effects of hyperglycaemia are similar to those of aldosterone on the cardiovascular system (CVS). In addition to its classical epithelial effects, aldosterone has a variety of non-epithelial effects including induction of inflammation, collagen formation, fibrosis and necrosis in the CVS. Interest in these effects has recently re-emerged. The three aldosterone antagonists currently licensed for use in the UK are: spironolactone, potassium canrenoate and eplerenone. Eplerenone is a selective aldosterone receptor antagonist. It is a derivative of spironolactone and has the major advantage of a lower incidence of androgenic and progestogenic side effects. Both spironolactone and eplerenone are effective antihypertensive agents and reduce mortality and morbidity in heart failure. They prevent sudden cardiac death. They also exert renoprotective effects. They should be judiciously used in diabetes due to their tendency for hyperkalemia, however, they have proved vital in providing a more complete inhibition of the deleterious effects of renin-angiotensin-aldosterone system (aldosterone antagonists).