The angiotensinogen (AGT) gene polymorphism M235T (a methionine to threonine amino acid substitution) has been investigated in association with essential hypertension (EHT) based on conventional measurement of blood pressure (BP); however, the results have been inconsistent. Recently, we have been conducting lines of genetic analysis on a general population of Ohasama Town in Iwate Prefecture, Japan, who measured their BP at home (Ohasama genetic analysis and home BP project). We here assessed the association between AGT M235T polymorphism and hypertension within the same population (1,245 subjects aged 40 years and over). AGT M235T polymorphism was determined by genotyping the AGT T+31C polymorphism, which has complete disequilibrium with the AGT M235T polymorphism. We defined subjects as hypertensive if they were being treated with antihypertensive medication and/or had home BP values of more than 135 mmHg in systole and/or 85 mmHg in diastole. The genotype frequencies were similar to those in previous Japanese studies. There was no significant difference among the genotypes in home BP values (p = 0.63/0.74 for systolic/diastolic blood pressure) or in prevalence of hypertension (MM: 44.7%; MT: 42.3%; TT: 39.6%; p = 0.61). No difference was noted in the frequency of familial history of hypertension. Pulse pressure, however, was significantly different among the genotypes (p = 0.049), and this association was prominent in the older (age260) population (p = 0.0018), but not noted in the younger population (60 > age > or = 40). In conclusion, the present analysis confirmed the lack of a significant effect of AGT M235T polymorphism on blood pressure level, but the difference in pulse pressure in the older population suggests that further investigations of this polymorphism should be made in the Japanese population.