This study investigated whether successive intranasal and intramuscular vaccinations administered to pigs when they were four and 10 weeks of age would reduce the circulation of Aujeszky's disease virus in eight persistently infected pig herds. The results of this strategy were compared with those obtained with the conventional two intramuscular vaccinations at 10 and 14 weeks of age. Piglets bom during a period of two weeks were vaccinated bythe new strategy and the piglets bom during the next two weeks were vaccinated according to the conventional schedule. The vaccine for intranasal administration consisted of 1O6-0 TCID560 of Kaplan gE-grstrain, suspended in 3 ml phosphate buffered saline. A commerdally available Bartha strain, suspended in an oil-in-water emulsion, was used for the intramuscular boostervaccination. At slaughter, the percentage of pigs with antibodies against glycoprotein E (gE), indicating infection with wild-type Aujeszky's disease virus was determined in both groups. Replication of the vaccine virus after the intranasal vaccination was demonstrated in both groups. Replication of the vaccine virus after the intranasal vaccination was demonstrated in 96 per cent ofthe pigs. Only 34 per cent ofthe pigs vaccinated by the new strategy showed a serological response (serum neutralisation titre ≥2) at 14 weeks of age. The percentage of slaughter pigs in the eight herds which had antibodies against gE after beingvaccinated bythe new strategy was 34.6 per cent, whereas 55.4 per cent ofthe pigs vaccinated conventionally had antibodies against gE.