Aujeszky's disease (AD) is increasing in Europe and it has become a serious problem in some of the countries of the European Communities (EC). The control and eradication of the disease is very difficult since AD virus (ADV) evokes a persistant latent infection in its main host, the pig. Such latent infection can also occur when vaccinated pigs are exposed to the virus. In view of this, the Commission of the European Communities (CEC) thought it necessary to have a survey on the current state of knowledge on AD and ADV. Therefore, a seminar was organised by the Federal Research Institute for Animal Virus Diseases in Tubingen, Federal Republic of Germany, and held there on June 9 and 10, 1981. The seminar was a part of the 'Animal Pathology Programme' of the CEC. The seminar was attended by 44 participants from the countries of the EC, and 29 papers were presented which covered a wide field of research on AD: properties of the virus, diagnostic procedures, immunity and pathogenesis, vaccination, latent infection, epidemiology, control and eradication. Scientists from differ- ent institutes in the EC who have been working on AD thus had the oppor- tunity to exchange their knowledge as well as to give and receive impetus for further scientific work. Furthermore, many details were given which are of interest for the veterinary authorities with regard to control and eradication of AD.