Abstract: Objective To compare the antihypertensive efficacy of irbesartan and losartan in patients with mild to moderate hypertension. Methods A randomized, double blind study was performed. After 2 week, single blind, placebo run in period, 72 patients with a mean seating diastolic blood pressure （SeDBP） of 95 to 115 mmHg were randomly allocated to receive either irbesartan 75 mg once daily （ n =36） or losartan 50 mg once daily （ n =36）. At week 4, if SeDBP was ≥90 mmHg, the daily dose was doubled to irbesartan 150 mg or losartan 100 mg. Results Blood pressure was significantly reduced in both groups （ P ＜0 01）. After 8 weeks of therapy, mean seated systolic blood pressure （SeSBP） and SeDBP were reduced by 15.0% and 13.3% respectively in irbesartan, 13.7% and 14.0% in losartan.\ There was no significant difference in the effective rate between irbesartan and losartan （75.0% vs 71.4%, P ＞0 05）. Losartan significantly reduced serum uric acid levels, whereas irbesartan showed little effect on uric acid. Conclusion Irbesartan is effective, safe. Its efficacy is similarto losartan in treating mild to moderate essential hypertension.