We assessed the prevalence of chronic kidney disease (CKD) in a hospital-based screening program in Okinawa, Japan. The significance of metabolic syndrome as a determinant of CKD was examined using multivariate logistic regression analysis. A total of 6980 participants, aged 30-79 years, participated in a screening program in Tomishiro Chuo Hospital. Metabolic syndrome was defined according to the criteria of the Adult Treatment Panel III (ATP III). Data were also analyzed according to the modified criteria of the National Cholesterol Education Program (NCEP) that defines abdominal obesity as a waist circumference of > oe =85 cm in men and > or =90 cm in women. CKD was defined as dipstick proteinuria (> or =1+) or a reduced glomerular filtration rate (GFR). GFR was estimated using the abbreviated Modification of Diet in Renal Disease (MDRD) formula. The prevalence of metabolic syndrome and CKD was 12.8 and 13.7%, respectively. Metabolic syndrome was a significant determinant of CKD (adjusted odds ratio (OR) 1.537 and 95% confidence interval (CI) 1.277-1.850, P<0.0001). The adjusted OR (95% CI) was 1.770 (1.215-2.579, P=0.0029) for those with four metabolic syndrome risk factors compared to those with no metabolic syndrome risk factors. Metabolic syndrome was a significant determinant for younger participants (<60 years; OR 1.686, 95% CI 1.348-2.107, P<0.0001), but not for older participants (> or =60 years; OR 1.254, 95% CI 0.906-1.735, NS). The relationship between the number of metabolic syndrome risk factors and the prevalence of CKD was linear using the modified criteria. The results suggest that metabolic syndrome is a significant determinant of CKD in men under 60 years of age, in Okinawa, Japan.