Aujeszky's disease virus (ADV) is a well known neurotropic virus in pigs. In the present study the mechanism of spread of ADV along the maxillary nerve and the role of the viral envelope glycoproteins gC, gE and gI in this process was examined in pigs. The Ka parental strain of ADV and its gC-, gE- and gI-deleted mutants were inoculated intranasally in pigs, after which virus dissemination in the maxillary nerve and the trigeminal ganglion was monitored at time intervals by means of virus isolation. The parental strain was isolated from both the nasal mucosa and the trigeminal ganglion at 21 h post-inoculation (p.i.), whereas the middle part of the connecting maxillary nerve was positive only after 48 h p.i. It appears, therefore, that ADV travels from the nasal mucosa via the nerve towards the ganglion in a non-infectious form, and then replicates in the neuronal somas, after which infectious virus is transported towards the nasal mucosa. Although all mutants were present at 48 h p.i. in the nasal mucosa and the trigeminal ganglion, the appearance of infectious virus in the maxillary nerve was clearly delayed with gE- and gI- mutants. It is suggested that glycoproteins gE and gI are involved in the axonal transport of infectious ADV away from neuronal cell bodies, also called anterograde transport.