More than other drugs, angiotension converting enzyme (ACE) inhibitors have been shown to provide better control of glomerular hypertension and improved preservation of renal function. Long-term treatment with captopril slows the progression of renal impairment in diabetic nephropathy; however, the data are inconclusive for non-diabetic nephropathies. ACE inhibitors such as captopril, enalapril, alacepril delapril cilazapril, and lisinopril were equally effective in reducing blood pressure in multicenter clinical trials focusing on renal hypertension in Japan. We studied the influence of ambulatory blood pressure (ABP) and the effects of hypertension therapy in 104 patients with chronic renal glomerulonephritis as diagnosed by renal biopsy. Patients were subdivided into hypertensive, normotensive and hypotensive groups according to ABP and ages. Hypotensive subjects showed an improvement, while normotensive subjects showed a slower rate of progression of renal function loss than hypertensive patients. This suggests that the adequate ABP levels were 100 to 125/55 to 75 in those who were less than 40 years old, 100 to 135/60 to 80 mm Hg in patients aged 40 to 60, and 105 to 140/60 to 85 mm Hg in those over 60 years old. The renal protective effects of calcium antagonists and ACE inhibitors were associated with a reduction in blood pressure, but not with the hypotensive action.