Metabolic syndrome is a risk factor for the development of cardiovascular disease. Few prospective studies, however, have examined metabolic syndrome as a risk factor for chronic kidney disease (CKD) in an Asian population. We studied the occurrence of CKD in 6,371 subjects without CKD or diabetes mellitus at baseline 1997 through 2002 in Okinawa, Japan. CKD was defined as dipstick-positive proteinuria (>or=1+) or a low estimated glomerular filtration rate (<60 mL/min/1.73 m2). Metabolic syndrome was defined according to the modified criteria of the Adult Treatment Panel III in which body mass index (>or=25 kg/m2) was substituted for the waist circumference measurement. Logistic analysis was used to analyze the effect of metabolic syndrome on the development of CKD. During the 5-year follow-up, 369 (5.7%) participants developed CKD. After adjusting for age, sex, current cigarette smoking and alcohol drinking habits at baseline, the relative risk of developing CKD was 1.86 (95% confidence interval: 1.43-2.41, p<0.0001) in subjects with metabolic syndrome. Compared with those without metabolic syndrome risk components, the adjusted relative risk (95% confidence interval) was 1.49 (1.10-2.01), 1.89 (1.38-2.59), and 2.65 (1.19-3.68) in those with 1, 2, or >or=3 metabolic syndrome risk components, respectively. Metabolic syndrome is a significant risk factor for the development of CKD in the Japanese population. Detection and treatment of metabolic syndrome should be stressed as a strategy to prevent CKD.