For the inspection of the occurrence situation of porcine pleuropneumonia and serotyping of Actinobacillus pleuropneumoniae strains isolated from lung lesions of pig in Korea, a series of experimentation have been carried out by the isolation and identification of A pleuropneumoniae, serotyping by coagglutination test, observation of lung lesion and clinical signs from 360 cases of porcine pneumonia in Clinical Pathology Laboratory, Bayer Veterinary Medical Research Institute. The results could be summarized as follows. The reaction of coagglutination between the reference antigens and the specific reagents of A pleuropneumoniae was strongly agglutinatied within 30 seconds without cross reaction. The 89 strains of A pleuropneumoniae were isolated from 360 cases of porcine pleuropneumonis and the biochemical properties of the isolates were same as the reference strains. The 89 isolated strains could be serotyped 39 strains as setotype 5, 34 strains as serotype 2, 8 strains as serotype 3, 2 strains as serotype 7 by coagglutination test, respectively. The clinical signs of pleuropneumonia were weakness, fever, anorexia, dyspnea and laboured breath in the later stages. The gross lesions of lung were haemorrhages, enlargement of interlobular septa, nodular formation and adhesion of the pleura.