In a study using the current first generation Ortho ELISA, a second generation Ortho ELISA, and the RIBA HCV strip immunoblot assay, all patients who were strongly positive for antihepatitis C virus (HCV) on ELISAs (OD490 > 3) were reactive to RIBA for multiple bands. While all ELISA false positive samples had low or intermediate OD490 values, RIBA confirmed HCV reactivity in 50% of the patients reactive to ELISA with a low suspicion of HCV infection, thus suggesting that RIBA HCV strip immunoblot assay will be most useful for patients who react weakly positive or intermediate to ELISA.