This study sought to investigate relationships between frequency of daily teeth brushing and prevalences of diabetes mellitus, hypertension and dyslipidemia. Subjects were 54,551 residents of Chiba City, Japan (20,155 men and 34,396 women) who underwent routine health examinations in 2004. Diabetes mellitus was defined as a fasting plasma glucose level > or =126 mg/dl or a non-fasting plasma glucose level > or =200 mg/dl and/or receiving treatment for diabetes. Hypertension was defined as systolic blood pressure (SBP) > or =140 mmHg, diastolic blood pressure (DBP) > or =90 mmHg and/or receiving treatment for hypertension. Dyslipidemia was defined according to the two criteria: high triglyceride and/or low high density lipoprotein cholesterol (TG > or = 150 mg and/or HDL-C < 40 mg/dl), and high total cholesterol (TC > or = 220 mg/dl). According to Pearson's chi-square tests and logistic regression analysis adjusted for age, BMI, smoking habit, alcohol consumption and daily walking time, lower frequency of teeth brushing is related to higher prevalences of diabetes mellitus, hypertension and high TG and/or low HDL-C, in both men and women. Total cholesterol status, however, showed no significant relationship. Maintaining good oral hygiene by regular teeth brushing may prevent type 2 diabetes, hypertension and dyslipidemia.