After a 4-week placebo baseline period, 29 Chinese elderly hypertensive patients were randomized, double-blind, to 12 weeks of treatment with either losartan potassium (n = 19), an angiotensin II antagonist at the AT1 receptor, or felodipine (n = 10), a calcium channel blocking agent. Of these 29 patients 12 had coexisting non-insulin-dependent diabetes mellitus. At week 12, the mean reductions (95% confidence intervals) in mean arterial pressure were similar in both groups: losartan -18 (range -22 to -14) mm Hg; felodipine -19 (range -25 to -11) mm Hg. In the whole group, the 24-hour urinary albumin excretion was reduced by 27% with losartan as compared with no change in the felodipine-treated group (p = 0.03; analysis of variance). In the diabetic group, losartan treatment reduced the urinary albumin excretion by 24% as compared with 11% in the felodipine-treated group. In the non-diabetic patients, the urinary albumin excretion fell by 29% in the losartan-treated group, but increased by 14% in the felodipine-treated group (p < 0.001; repeated-measures analysis of variance). Plasma sodium increased to a similar extent in both groups. The fasting plasma triglyceride level declined by 25% (p < 0.001 within group) with losartan, but was not significantly reduced in the felodipine-treated group. For comparable reductions in blood pressure, a greater reduction in albuminuria was seen with losartan than with felodipine treatment in Chinese hypertensive patients with or without non-insulin-dependent diabetes mellitus. Long-term studies are required to examine whether these antiproteinuric effects of losartan can be translated to renoprotection.