The renin-angiotensin-aldosterone system has an important role in the progression of both diabetic and nondiabetic nephropathy. Angiotensin-converting enzyme inhibitors and angiotensin-II receptor blocker can effectively retard or halt this progression. However, their renoprotective effect is not enough, because approximately 20% of patients have a progressive course to endstage renal disease. There is now clear evidence that combination therapy of two agents is more antiproteinuric and, likely renoprotective, than each agent alone. However, several critical issues should be addressed before recommending it as standard treatment in chronic renal disease.