In order to investigate the contribution of candidate genes in the renin-angiotensin- -aldosterone system (RAAS) in pathogenesis of essential arterial hypertension (EAH), the I/D polymorphism of ACE gene, the M235T polymorphism of the angiotensinogen gene, and the angiotensin II type 1 receptor (AGT1R) A1166C gene polymorphism in a group of children with EAH were analyzed. Fifty-seven children, aged 8-19 years, with the diagnosis of EAH were included in the association study and were compared with 57 subjects with normal blood pressure (the control group). Arterial hypertension was defined as systolic/diastolic blood pressure measurements higher than 95 age-gender-height percentile of the adopted reference values. A trend was found towards an association between the M235T angiotensinogen gene polymorphism and EAH in childhood in a dominant model (odds ratio (OR) 2.1; 95 % confidence interval (CI) 0.9-5.1; P=0.077), whereas the authors failed to demonstrate an association between the ACE I/D gene polymorphism, or the A1166C AGT1R gene polymorphism and EAH in childhood. Additionally, evidence was found of interaction between the angiotensinogen-TT genotype and obesity on the risk of EAH in childhood (OR 19.3; 95% CI 1.1-77.3; P=0.014). In conclusion, the M235T angiotensinogen gene polymorphism is considered alone as well as in interaction with obesity to be risk factors for EAH in childhood.