A 24-year-old Japanese woman with IgA nephropathy was admitted to our hospital due to the development of proteinuria and pretibial edema while on glucocorticoids and an angiotensin-converting enzyme (ACE) inhibitor. She had been on both medications for more than 2 years. Urinary protein excretion was 2.53 g/day and renal function laboratory data were within the normal range. Plasma aldosterone concentration was high at 248 pg/ml, with normal plasma renin activity. The renal biopsy specimens showed prominent glomerular hypertrophy. Four weeks after the addition of valsartan, an angiotensin IIreceptor blocker (ARB), urinary protein excretion was remarkably reduced to 0.6g/day without adversely affecting blood pressure. During the treatment period, proteinuria was maintained at less than 0.6g/day and renal function remained normal. We propose that glomerular hypertension caused by insufficient suppression of the renin-angiotensin system was an essential factor underlying the increased urinary protein excretion in this patient. Combination therapy of an ARB and an ACE inhibitor appears to have a beneficial effect in patients with IgA nephropathy patients with persistent glomerular hypertension.