Hypertension and obesity are likely the most common disease in Japan. It has been reported that subjects with prehypertension (systolic blood pressure [SBP] 120-139 mmHg and/or diastolic blood pressure [DBP] 80-89 mmHg) have also an increased risk of cardiovascular disease; however, only limited data are available on the prevalence of prehypertension and its association with body weight. We performed a cross-sectional study to examine whether the status of body weight was associated with prehypertension. Study participants aged 19 to 90 years [1,207 men aged 60 +/- 15 (mean +/- standard deviation) years and 1,634 women aged 63 +/- 12 years] were randomly recruited for a survey at the community-based annual medical check-up. The prevalence of prehypertension was 27.3% in men and 23.9% in women. The levels of SBP and DBP increased, as body mass index (BMI) increased in both genders. In a multivariate-adjusted model, increasing BMI categories were positively associated with prehypertension. Especially in men, compared to participants with BMI of < 21.0 kg/m(2) (referent), the multivariate-odds ratio (95% CI) of prehypertension was 1.90 (1.17-3.09) in the 21.0-23.4 kg/m(2) group, 2.38 (1.31-4.34) in the 23.5-24.9 kg/m(2) group, and 3.79 (2.03-7.09) in the > or = 25.0 kg/m(2) group. In conclusion, even subjects with mildly increased BMI (21.0-24.9 kg/m(2)) had an increased risk of prehypertension in community-dwelling persons. It is time to pay more attention to excess bodyweight in preventing high blood pressure.