Abstract: Objecfive To compare the effects of fix-combination with simple combination on the antihypertensive activity and compliance.Methods Totally 160 patients with initial mild-moderate essential hypertension were randomized into two groups:fix-combination or simple combination with irbesartan and hydrochlorothiazide groups.The antihypertensive activity and tolerability within three months were monitored.Results Compared with simple combination(141.3±5.7)mm Hg and(85.5±3.8)mm Hg,fix-combination(139.4±3.6)mm Hg and (83.2±2.1)mm Hg did not further decrease the systolic and diastolic blood pressure within 1 month's treatment (P>0.05).However,3 months later,the systolic blood pressure,the rate of reaching blood pressure target and tolerability were improved more in fix-combination group than that in simple combination group(all P<0.05).Conclusion Fix-combination antihypertensive therapy can increase antihypertensive activity and tolerability in patients with initial mild-moderate essential hypertension.