Sera of 20 children falsely identified as positive for hepatitis C virus antibody (Anti-HCV) by a second generation anti-HCV-assay kit (Imucheck-HCV Ab "Kokusai") were re-tested using a new third generation anti-HCV-assay kit (Imucheck x F-HCV C50 Ab "Kokusai"). Seventeen of the samples were reclassified as negative and only three remained positive. Changing well solids in the anti-HCV-assay kit from casein to bovine serum albumin appears to have improved the false-positive rate, most likely as a result of decreased non-specific adsorption of casein antibodies.