Veterinary Immunology has become a valuable link in the field of veterinary research. Recent developments in veterinary immunology in the Department of Immunochemistry of the Central Veterinary Institute are reviewed. In 1978, Counter Immuno-Electrophoresis was introduced for the diagnosis of Aleutian Disease (AD) in mink. Since then, more than 100,000 sera were tested (1). It is not clear whether the enormous amounts of specific anti-AD antibodies found in the serum of diseased mink have a biological significance. The present author recently developed an indirect haemagglutination test for the diagnosis of Dictyocaulus viviparus infection in cattle. The test compares favourably with the parasitological diagnostic methods so far used (2). The interpretation of levels of specific and anti-D. viviparus antibodies continues to be open to discussion, and the question whether antibodies are induced by larvae and/or other developmental stages of D. viviparus is still unanswered. With regard to E. coli infections, the question is asked whether research on 'minimum' vaccination against E. coli during the first day of life may help to reduce diarrhoea in weaner pigs. As intradermal injections resulted in significantly higher antibody titre in an anti-bovine albumn-immunisation model in pigs, alternative modes of immunisation are worth investigating. Recent developments in the production and use of class-specific antibodies are reviewed (3, 4).