Angiotensin receptor blockers (ARBs) are the recommended first-line antihypertensive treatment for managing chronic kidney disease, and strict blood pressure (BP) regulation is crucial for the reduction of proteinuria. Valsartan and candesartan are commonly used ARBs in Japan, with maximum permissible doses of 160 mg/day and 12 mg/day, respectively. We evaluated BP and proteinuria after changeover from the maximum dose of candesartan to the maximum dose of valsartan, in 55 poorly controlled hypertensive patients undergoing candesartan treatment who were unable to achieve optimal BP according to the Japanese Society of Hypertension Guidelines for the Management of Hypertension (JSH 2004). We measured BP and pulse rate and assessed urinary protein excretion (UPE) before and after changeover. Changeover was associated with decreases in systolic BP and diastolic BP from 158/89 mmHg to 150/86 mmHg (p<0.01). Changeover was also associated with a reduction in UPE adjusted to urinary creatinine from 0.35+/-0.19 g/g creatinine to 0.19+/-0.37 g/g creatinine (p=0.0271) in patients who had high urinary protein levels prior to changeover without significant decreases in BP (p=0.0184). According to multiple regression analysis, higher UPE (p<0.0001) and a lower glomerular filtration rate (GFR) (p=0.0011) prior to changeover were independently correlated with reduction in UPE. Our results suggest that the maximum dose of valsartan is more effective than the maximum dose of candesartan for reducing BP and proteinuria.