Previous research supports an association between hepatitis C virus (HCV) infection and glomerulonephritis. However, little is known about the association between HCV and chronic kidney disease. The cross-sectional association between prevalent hepatitis C seropositivity and albuminuria and estimated GFR (eGFR), respectively, was examined among 15,029 participants in the Third National Health and Nutrition Examination Survey (NHANES III). In the multivariate analysis, we noted an age-dependent association between HCV seropositivity and albuminuria (adjusted odds ratios and 95% confidence intervals 0.83, 0.39 to 1.75 for ages 20 to 39; 1.84, 1.00 to 3.37 for ages 40 to 59; 2.47, 1.27 to 4.80 for > or =60 yr of age). There was no significant association observed for hepatitis C seropositivity and low eGFR (<60 ml/min per 1.73 m(2); adjusted odds ratios and 95% confidence interval for all ages 0.89, 0.49 to 1.62). Among a representative sample of the US population, hepatitis C is independently associated with albuminuria among adults over the age of 40; however, it does not seem to be significantly associated with a low eGFR in this population-based cross-sectional analysis.