Low-grade albuminuria has been proposed as a cardiovascular risk factor that is below the conventional cut-off point for microalbuminuria, which has been previously identified as a marker for cardiovascular disease and chronic kidney disease (CKD). Metabolic syndrome has also been shown to be related with microalbuminuria and CKD. We assessed the relationship among low-grade albuminuria, CKD and metabolic syndrome among 5998 non-diabetic subjects. The subjects were divided into six groups: subjects with urine albumin-to-creatinine ratio (UACR) <30 mg g(-1) were divided into five groups in accordance with their UACR values, and subjects with 30<or=UACR <300 mg g(-1) were allocated to the microalbuminuria group. The prevalence of CKD increased in parallel with increasing UACR values and greater numbers of metabolic syndrome characteristics, which were in turn associated with a reduced UACR cut-off point for an increased prevalence of CKD. Among the subjects with metabolic syndrome, UACR values above 10.2 mg g(-1) were related to increased CKD prevalence (odds ratio (OR): 2.63, 95% confidence interval (CI) 1.11-6.24), as were values of 30 mg g(-1) among those with 1 or 2 components of metabolic syndrome (OR: 2.98, 95% CI 1.83-4.83); elevated UACR was not observed to increase the risk of CKD in subjects who had no components of metabolic syndrome. The cut-off point varied in subjects with various cardiovascular risk profiles such as serum uric acid level, gender or hypertension. Very low levels of albuminuria were associated with increased CKD prevalence. The UACR cut-off point for increased CKD risk varied according to the risk profile, including the number of metabolic syndrome components.