A case of bilateral encephalomalacia in a pig related to latent Aujeszky's disease virus infection is reported. The pig was experimentally inoculated with the NIA-3 strain and survived the infection after showing intense central nervous system disease. Abnormal behaviour was observed up to the date of death. The pig was demonstrated to be latently infected with the virus by polymerase chain reaction (PCR). The main microscopic lesion was a bilateral encephalomalacia which involved structures related to the limbic system. A complete description of lesions observed and their relation to abnormalities shown by the pig are exposed.