Sixteen pigs aged 5 to 7 weeks were inoculated intranasally with the pneumotropic strain 4892 of Aujeszky's disease virus (ADV) in a dose of 2 x 105 TCID50. Pigs died or were killed on day 4, 5, 6, 7, 8, 10, 12, 20 or 30 post-inoculation (PI). Two further pigs were kept as negative (uninfected) controls. Histopathological examination demonstrated meningoencephalitis, necrotizing rhinitis and multifocal systemic necrosis. Viral antigen was detected immunohistochemically, mainly in the central nervous system up to day 12 PI, and to a lesser degree in the lung, nasal mucosa and tonsil. ADV DNA was detected at days 20 and 30 PI by a nested polymerase chain reaction technique. This study indicated that the spread of the highly virulent, pneumotropic strain 4892 did not differ from that of other neurotropic or pneumotropic ADV strains.