A new enzyme-linked-immunosorbent assay (ELISA) for the detection of antibodies to feline immunodeficiency virus was compared with previously described ELISAs. Serum samples from 184 infected or uninfected cats were tested using a whole virus lysate kit and ELISAs based on recognition of one of two synthetic peptides (P237 and P253) localized in the transmembrane domain of the viral envelope. The whole virus lysate commercial kit led to the detection of 6% false positive and 4.3% false negative sera. The ELISA based on peptide P253 gave no false positive result and failed to detect only one serum that was subsequently shown to be positive by radio-immunoprecipitation assay. A sandwich-ELISA test using Galanthus nivalis agglutinin, a lectin that specifically binds terminal mannose groups of the envelope proteins was used as a confirmatory test for equivocal results with peptide ELISA and gave similar results. This study indicates that recognition of P253 could serve as a sensitive and specific test for the diagnosis of seropositivity to feline immunodeficiency virus, and moreover that the Galanthus nivalis ELISA could be useful in equivocal cases as a confirmatory test.