A multiplex-PCR assay was developed to identify Actinobacillus pleuropneumoniae (App). Two pairs of polymerase chain reaction (PCR) primers were designed for the 16S rRNA and the apxlVA gene, which is specific to all serotypes of App. Two PCR products of 692bp and 363bp were obtained, from the 16S rRNA and the apxlVA gene respectively, for 27 reference A. pleuropneumoniae strains. Only the 692bp fragment was amplified for closely related strains including A. lignieresii. Using the designed primers, the method is capable of detecting A. pleuropneumoniae of as low as 1.3 x 10(3) CFU or 9pg DNA. For 302 suspected isolates, this multiplex-PCR method correctly identified 4 A. pleuropneumoniae strains. The result suggests the use of the multiplex-PCR for routine identification of App.