Background: The American Heart Association/National Heart, Lung, and Blood Institute (AHA/NHLBI), revising the National Cholesterol Evaluation Program for Adult Treatment Panel III (NCEP ATP III), and the International Diabetes Federation (IDF) have proposed defi nitions of metabolic syndrome that take into account waist circumference thresholds according to ethnicity. In this study we estimated the prevalence of metabolic syndrome in a Japanese-Brazilian population using NCEP defi nitions for Westerners (NCEPwe) and Asians (NCEPas), and IDF for Japanese (IDF). Methods: A total of 650 Japanese-Brazilians living in a developed Brazilian city and aged 30-88 years were included. Results: Metabolic syndrome prevalence according to NCEPwe, NCEPas, and IDF was, respectively, 46.5%, 56.5%, and 48.3%. Only 43.5% of subjects did not have metabolic syndrome by any of the 3 defi nitions, and 38.3% fulfi lled metabolic syndrome criteria for all 3 defi nitions. Ten percent of subjects were positive for metabolic syndrome based on NCEPas and IDF, but not for NCEPwe. Because IDF requires abdominal obesity as a criterion, the frequency of subjects without metabolic syndrome according to IDF, but with metabolic syndrome by NCEPwe and NCEPas was 8.2%. Conclusions: Independent of the metabolic syndrome defi nition, Japanese-Brazilians present an elevated metabolic syndrome prevalence, which was higher when using NCEP criteria for Asians, followed by the IDF defi nition for Japanese.