Mice with defects in the Klotho gene exhibit multiple aging phenotypes including arteriosclerosis. We hypothesised that the G-395A polymorphism in the promoter region of the human Klotho gene may contribute to the prevalence of Essential Hypertension (EH).We investigate whether the G-395A polymorphism of Klotho is associated with EH in a population consisting of 215 patients with EH and 220 non-hypertensive subjects. We also tested whether a G/A substitution at the G-395A site affected the transcription level in vitro through the dual-luciferase reporter assay.Differences in the genotype distributions of the G-395A polymorphism between the EH and non-hypertension groups are statistically significant (P=0.032). There are differential effects of age, gender and smoking status on the association of the G-395A polymorphism with EH; the G-395A polymorphism is significantly associated with EH in subjects over 60years old, in females and in nonsmokers. A multiple logistic regression analysis indicated that the odds ratio for EH in the –395A allele carriers as compared with the control group was 0.593 (P=0.024) after adjusting for current traditional risk factors. The dual-luciferase reporter assay revealed that the –395A carrier of a 498-bp DNA fragment (containing the G-395A site) upstream of the Klotho gene has higher relative luciferase activity than the –395G carrier.The G-395A polymorphism of the human Klotho gene is associated with EH and may be a potential regulatory site.