Fil: Riera, L M. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Fil: Feuillade, M R. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Fil: Saavedra, M C. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Fil: Ambrosio, A M. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.To elaborate a set of serological tests for the diagnosis of Argentine haemorrhagic fever (AHF), an enzyme-linked immunosorbent assay (ELISA) for detection of specific anti-Junin virus (JV) IgG is described, and its performance is compared with that of the plaque reduction neutralization test (PRNT). The reproducibility, sensitivity, specificity, and confidence limits for positive and negative results for ELISA were statistically analysed. The value of 800 was demonstrated as the lowest positive titer. Titers > or = 800 varied within one (two-fold) dilution in 95.6% of the tests, while the sensitivity and specificity were 99.2% and 98.8%, respectively. The assay yielded 1% of false positives and 0.05% of false negatives. A comparison of ELISA to PRNT in detecting the seroconversion for JV was studied by the chi square test (comparison of proportions in paired samples) and the K parameter for agreement proportion. Comparison of ELISA to PRNT showed no significant difference in the proportions of positive and negative results of these assays (P < 0.01), demonstrating an equivalent performance (K = 0.98) in the diagnosis of AHF. In addition, the simplicity and safety of the procedures involved make this ELISA the most suitable test to detect natural human JV infections.