Clinical and epizootiologic studies have been carried out in the course of one year on a farm with a permanent Aujeszkys disease infection as well as virologic and serologic investigations, performed seven times, with a total of 70 fattened pigs. No clinical symptoms of Aujeszky's disease have been established during the period of investigation, while the epizootiologic status have invariably spoken of the fact that the infection had a stationary course on this farm. The virus was isolated from meat and bone marrow, which posed the question of veterinary and sanitary inspection of meat obtained from such animals. The virologic results were varying by months, the peak percent values of positive animals and organs being established over the winter-spring period. Serologically, the results have agreed with the findings in the virologic studies: most significant were the variations in the months during which there was a highest percent of positively reacting animals and organs. It has been assumed that the disease was maintained in a latent form on the farm investigated, showing certain variations as to its manifestation, with no trend in terms of spontaneous recovery.