The aim of these studies was to determine the performances of five commercial ELISA kits in the detection of BLV antibodies in serum samples. Different variants of ELI SA methods (indirect, blocking and double-well) were employed for these kits. Comparative investigations using 428 serum samples showed 418 consistent results (97.7%). Ten results (2.3%) proved to be inconsistent including 7 (1.6%) results which were totally different. The cause of these divergences in serological tests are discussed.