Background The renin-angiotensin-aldosterone system (RAAS) is important for the development of essentialhypertension,and many antihypertensive drugs target it.This study was undertaken to determine whetherpolymorphisms in the renin-angiotensin-aldosterone system are related to the blood pressure (BP) response to diuretictreatment in a Chinese Hart ethnic population.Methods Fifty-four patients with essential hypertension received hydrochlorothiazide (12.5 mg,once daily) asmonotherapy for four weeks.Seven polymorphisms in RAAS genes were genotyped by gene chip technology.Therelationship between these polymorphisms and the change in blood pressure was observed after the 4-week treatment.Results The patients with angiotensinogen (AGT)-6G allele showed a greater reduction in diastolic BP (P=0.025)and mean BP (P=0.039) than those carrying AA genotype.Patients carrying aldosterone synthase (CYP11B2) CCgenotype exhibited a greater BP reduction than those carrying CT and TT genotypes (systolic BP:P=0.030;diastolicBP:P=0.026;mean BP:P=0.003).In addition,patients with a combination of CYP11B2 CC genotype and angiotensinconverting enzyme (ACE) D allele might have a more pronounced reduction of systolic BP than those with any othergenotypic combinations of the two genes (P=0.007).Conclusions AGT-6G allele,CYP11B2-344CC genotype and its combination with ACE D allele are associated withBP response to hydrochlorothiazide treatment.Larger studies are warranted to validate this finding. Background The renin-angiotensin-aldosterone system (RAAS) is important for the development of essential hypertension, and many antihypertensive drugs target it. This study was undertaken to determine whether polymorphisms in the renin-angiotensin-aldosterone system are related to the blood pressure (BP) response to diuretictreatment in a Chinese Hart ethnic population. Methods Fifty-four patients with essential hypertension received hydrochlorothiazide (12.5 mg, once daily) asmonotherapy for four weeks. Seventh polymorphisms in RAAS genes were genotyped by gene chip technology. Relationship between these polymorphisms and the change in blood pressure was observed after the 4-week treatment. Results The patients with angiotensinogen (AGT) -6G allele showed a greater reduction in diastolic BP (P = 0.025) and mean BP (P = 0.039) than those carrying AA genotype. Patients carrying aldosterone synthase (CYP11B2) CC genotype exhibited a greater BP reduction than those carrying CT and TT genotypes (systolic In addition, patients with a combination of CYP11B2 CC genotype and angiotensinconverting enzyme (ACE) D allele might have a more pronounced reduction of systolic BP than those (P = 0.030; diastolic BP: P = 0.026; with any other genotypic combinations of the two genes (P = 0.007). Conclusions AGT-6G allele, CYP11B2-344CC genotype and its combination with ACE D allele are associated with BP response to hydrochlorothiazide treatment. Larger studies are warranted to validate this finding.