The therapeutic importance of inhibitors of the RAS, such as converting enzyme inhibitors, is based on their cardioprotective as well as antiproliferative effects and points to a direct involvement of the RAS in the development and preservation of primary hypertension, a pathological condition in which normal or even low plasma renin activity is a common finding. Reversal of cardiovascular structural changes and enhancement of renal sodium excretion by converting enzyme inhibitors are important long-term antihypertensive actions possibly mediated by inhibition of the tissue RAS.