The diagnostic performances of three commercially available recombinant immunoblot assays (RIBAs) for anti-hepatitis C virus antibody were evaluated on 50 ORTHO-HCV RIBA-2 (RIBA-2)-indeterminate serum samples. Concordant interpretations were obtained with the three tests in 60% of the samples, with 56% positive, 2% indeterminate, and 2% negative results. Considering test performance in regard to the number of remaining indeterminate results, analyzing sera by RIBA-3, INNO-LIA HCV Ab III, and DECISCAN HCV reduced the number of samples reacting indeterminately to 40, 6, and 8%, respectively. The three serum samples classified as indeterminate in the INNO-LIA HCV Ab III as well as three of four serum samples interpreted as indeterminate in the DECISCAN HCV and 16 of 20 samples classified as indeterminate in the RIBA-3 were hepatitis C virus RNA positive by PCR. This study clearly shows the good performance of the three tests as confirmatory assays compared with that of the RIBA-2. However, according to the manufacturers' criteria of positivity, the INNO-LIA HCV Ab III and DECISCAN HCV appeared to be more suitable than the RIBA-3 for interpreting serum samples found indeterminate in the RIBA-2.