Development of enteric lesions in closed jejunal and ileal loops inoculated with Aujeszky's disease virus (ADV) was examined in four 6-week-old SPF pigs. A large number of ADV antigens were detected first in necrotic foci in the subepithelial areas, and subsequently in the epithelial cells, lymphoid follicles in Peyer's patches and neuronal cells of Meissner's and Auerbach's plexuses.