This study was designed to determine if GR 32191, a thromboxane A2 receptor antagonist, would lower blood pressure in patients with hypertension and renal artery stenosis. Eight patients with unilateral atheromatous renal artery stenosis and hypertension were studied in a double-blind, single dose, placebo controlled, crossover study. The results show that, GR 32191, given orally, in doses of 20 mg and 40 mg, does not reduce the blood pressure to any clinically important degree.