A new 4-antigen recombinant immunoblot assay (4-RIBA) for confirmation of hepatitis C virus (HCV) C-100 enzyme-linked immunosorbent assay (ELISA) reactivity was tested in serum samples of 11 pediatric patients on dialysis. Of 6 HCV C-100 ELISA-positive samples, all were 4-RIBA positive. The 2nd generation ELISA picked up 1 additional case confirmed by 4-RIBA. The 2nd generation tests increased the prevalence of HCV-positive cases.