Objective:To study the relationship between G protein ? 3 subunit ( GNB3 )C825T variant and plasma renin angiotensin system(RAS) activity in Chinese essential hypertensive patients. Methods: Case control method was used. For 408 essential hypertensive patients who were enrolled in the trial groups, we chose 140 normotensives as control group 1 and 61 health persons with hypertensive familial history as control group 2, respectively. PCR-RFLP method was used to measure the C/T polymorphism. The results were observed by agarose gel eletrophoresis. Results: The frequencies of 825T allele were 45.6% to 56.4% in the three groups. Neither GNB3 genotype distribution nor the frequency of T allele was associated with essential hypertension. But patients with TT genotype had higher aldosterone level and lower angiotensin converting enzyme (ACE) activity than patients with CC genotype. Conclusion:In Chinese, patients with TT genotype had higher aldosterone level and lower angiotensin converting enzyme (ACE) activity.