All components of the renin-angiotensin system are present in the kidneys. Angiotensin II production is specifically regulated within the kidneys, and this regulation may differ from that operating in plasma or, possibly, in other organs. Coordination between renin synthesis and release (locally influenced by angiotensin II levels) and the activity of many proteins involved in sodium epithelial transfer, may be imperfect and contribute to create a high basal blood pressure which, in the long term, accelerates the onset and progression of cardiac, vascular and renal lesions.