Recently it has been recognized that even minor elevations of blood pressure contribute to progression of renal failure. Furthermore it has been documented that antihypertensive treatment retards progression of renal failure. Despite impressive experimental data firm clinical evidence, incontrovertible on biostatistical grounds, is not yet available to document that converting enzyme inhibitors (CEI) are superior to alternative antihypertensive agents with respect to halting progression. CEI undoubtedly reduce albuminuria, independent of their effect on systemic blood pressure, and this is related to alterations of glomerular permeability. Recent experimental data suggest that growth processes in damaged kidneys are an important aspect of progression. It is a fascinating perspective, but yet unproven, that CEI interfere with these processes.