Background To clarify whether there are age and gender differences in the components contributing to the diagnosis of metabolic syndrome (MS) in the Japanese population. Methods and Results A total of 21,870 individuals (ie, 7,329 men aged 68±8.1 years, body mass index (BMI) 23.2±2.9 kg/m² and 14,541 women aged 66±9.4 years, BMI 22.8±3.3 kg/m²) participated in the study. The subjects were obtained from the general population and examinations were conducted in hospitals located in Kanazawa city. MS was diagnosed according to the Japanese criteria. Information regarding medication is lacking in all participating subjects. Overall, the incidence of MS was 18.4% and 5.78% for men and women, respectively. When analyzed according to age group, the incidence of MS in men did not differ significantly, whereas its prevalence was higher in older women than in younger women. Among the indicators of MS, high blood pressure (BP; high systolic BP and/or high diastolic BP) was the most frequent, followed by dyslipidemia (high triglycerides and/or low high-density lipoprotein-cholesterol (HDL-C)), and high fasting plasma glucose was the least frequently occurring in both genders. In contrast to the high frequency of high BP, isolated high diastolic BP was rare across both genders regardless of age group. Similarly, isolated low HDL-C was quite rare. Conclusions Frequency of the components contributing to the diagnosis of MS differed considerably according to gender and age group in the Japanese population. (Circ J 2007; 71: 1734 - 1737)