CS-866, a novel angiotensin II receptor blocker, is rapidly and completely metabolized to RNH-6270, its active metabolite. The pharmacokinetics of RNH-6270 following oral CS-866 or intravenous RNH-6270 administration was determined in 104 healthy male volunteers. The pharmacokinetics of RNH-6270 was linear over dose ranges of 1 to 32 mg (intravenous RNH-6270 administration) and 10 to 160 mg (oral CS-866 administration). The time to maximum plasma concentration of RNH-6270 after oral CS-866 administration ranged from 1.4 to 2.8 hours, and the terminal elimination half-life ranged from 12 to 18 hours. Absolute bioavailability of RNH-6270 after oral administration of CS-866 was 26%. Administration of CS-866 once daily for 10 days did not result in drug accumulation. When administered intravenously, RNH-6270 has a volume of distribution of 15 to 25 L. Approximately 35% to 50% of RNH-6270 is excreted unchanged in the urine. CS-866 was safe and well tolerated at doses of up to 160 mg/day.