Two enzyme-linked immunosorbent assays (ELISAs) for the diagnosis of bovine virus diarrhoea (BVD) are described: CHEKIT-BVD-VIRUS and CHEKIT-BVD-SERO. The first test detects virus antigen in leucocytes, resulting in identification of persistently-infected animals, while the second detects antibodies to BVD virus (BVDV). It is well known that even persistently-infected animals may have antibodies to heterologous BVDV strains. These animals are still negative to the CHEKIT-BVD-SERO test because of immunotolerance to conserved virus antigens. Data on these two tests are summarised and a scheme is presented for the diagnosis of BVD using a combination of these two tests.