Although multiple antihypertensive agents are required to control blood pressure (BP) in chronic renal disease, it remains undetermined whether the combination therapy with angiotensin receptor blockers (ARB) plus calcium antagonists or angiotensin-converting enzyme inhibitors (ACEI) confers more preferable action on renal disease than the ARB monotherapy. In the present study, we compared the effect of the combination therapy with ARB plus calcium antagonists/ACEI on proteinuria with that of the ARB monotherapy in chronic nondiabetic renal disease. At 1 month of the drug treatment, the candesartan monotherapy (n=19) reduced BP from 154+/-3/93+/-2 to 146+/-3/88+/-2 mmHg (P<0.05), and a similar magnitude of BP reductions was observed with the combination therapy with candesartan plus ACEI/amlodipine (from 153+/-2/95+/-2 to 144+/-2/88+/-2 mmHg, P<0.05, n=39). The depressor action of these therapies was sustained throughout the 12-month treatment. In contrast, the reduction in proteinuria was greater with the combination therapy (-52+/-3% at 12 months, n=39) than with the candesartan monotherapy (-25+/-3%, n=19), although the baseline values of proteinuria were nearly the same in the candesartan monotherapy group (1.74+/-0.22 g/day) and the combination therapy group (2.10+/-0.19 g/day, P>0.2). Of note, the proteinuria-sparing effect did not differ between the candesartan+ACEI group and the candesartan+amlodipine group. In conclusion, the present study suggests more beneficial action of the combination therapy with ARB plus ACEI/amlodipine than the ARB monotherapy in nondiabetic renal disease. Since the reduction in BP was achieved to the same level, the distinct proteinuria-sparing action of these therapies is attributed to BP-independent mechanisms, which should vary depending on the agents used.