We investigated whether a selective angiotensin II receptor blocker (ARB) would have a regressive effect on left ventricular hypertrophy (LVH) in patients on continuous ambulatory peritoneal dialysis (CAPD). In a double-blind study, 24 CAPD patients with LVH [left ventricular mass index (LVMi) > 110 g/m2 for women and LVMi > 137 g/m2 for men] were randomized to 12 months' administration of either the ARB valsartan (n = 14) or a placebo (n = 10). The target blood pressure (BP) was 140/90 mmHg or lower in both groups. The following parameters were measured before and at the end of the study: aortic and large-artery compliance and arterial wave reflections [pulse wave velocity (PWV) and augmentation index (AI) application tonometry] and cardiac echocardiography. Periodically recorded were body weight, BP (mercury sphygmomanometer), serum creatinine, electrolytes, complete blood cell counts, urine volume, drainage volume, and weekly creatinine clearance. Two-way analysis of variance for repeated measurements was used for statistical analysis. Systolic and diastolic BP were both reduced in patients treated with ARB. The LVMi was significantly reduced in patients treated with ARB (to 121 +/- 4 from 145 +/- 5) but not in those receiving placebo (to 137 +/- 3 from 152 +/- 3, p < 0.05). The decrease in LVMi was associated with a reduction in PWV and AI. In CAPD patients with LVH, ARB reduced LVMi in association with alterations in arterial hemodynamics.