28 Pasteurella multocida strains were examined for production of toxin by 6 different methods. Identical results were obtained using a mice lethality test, a tissue cell culture assay and an ELISA. Different results were received with a dot-blot-immunoassay (1 strain), using a gene probe (6 strains) and a guinea pig skin test (8 strains). Corresponding differences were detected with 2 strains only. Tissue culture, ELISA and dot-blot-immunoassay are effective methods for the diagnosis of toxin-producing Pasteurella multocida strains. Animal experiments should be an exception.