A woman bought two ferrets from a pet shop. These ferrets became brutal soon, excreted a large amount of saliva and then died. One of these ferrets had bitten the owner's hand before it died. As for the ferret, rabies and distemper were suspected. To receive rabies post-exposure prophylaxis the woman visited our vaccine clinic. To clarify the ferret's cause of death virological examinations were requested to Tokyo Metropolitan Institute of Public Health. The rabies examination of the ferret that had bitten the owner was performed according the law. However the tests of the other ferret that had not bitten the owner was not done though it was suspected to die from rabies, because the law does not mention such a case like the latter ferret. The virological tests concerning distemper were not accepted by the Institute, so the examination was done at a private laboratory. These two ferrets were diagnosed to have had distemper from the results. It is clearly shown from this biteaccident that the legal system where the cause of the animal's death required is extremely incomplete in Japan.