Angiotensin II type 1 (AT1) receptor mediates the vasoconstriction and growth-promoting effect of angiotensin II in humans. It has been reported that a polymorphism of the AT1 receptor gene (an A/C transversion at position 1166; A1166C) may be associated with essential hypertension (HT). However, several conflicting results have also been reported. Therefore, we conducted an association study between A1166C variants of the AT1 receptor gene and hypertension in the Japanese population. We genotyped this variant in 3,918 subjects (1,492 hypertensive subjects and 2,426 normotensive subjects) recruited from the Suita study. In subjects not receiving antihypertensive medication, the influence of the genotype on blood pressure values adjusted for clinical covariates was analyzed. The genotype distribution did not differ between hypertensive and normotensive subjects in either men (frequency of the C allele: 8.1% vs. 7.8%, p=0.74) or women (8.1% vs. 7.7%, p=0.60). There were no significant differences in systolic blood pressure, diastolic blood pressure, or pulse pressure among the three genotypes in either men or women who had not received hypertensive medication. Our data suggest that the A1166C polymorphism of AT1 receptor is unlikely to influence blood pressure status in the Japanese population.