In recent years much attention has been paid to swine respiratory infection caused by Pasteurella(P) multocida with rapid expansion of pork Industry in Korea. The present study was performed to observe the etiologic situation of P. multocida infection by bacteriological, serological(serotyping) and pathological examinations with the lungs respectively. In addition antibiotic susceptibility test was carried out against the isolated strains of P. multocida. The results obtained are as follows : 1. Eighteen strains(12.8％) wert isolated from the 140 cases of swine lungs examined, and biological and biochemical characteristics of the isolates were the sam as those in the references of other workers, whereas some differences were observed in sugar fermentation and enzyme activity according to the strain of isolates. 2. Capsular serotyping performed on 18 P. multocida revealed that 13 strains(72.2％) were A type and 5 strains(27.8％) were D type, respectively. 3. When serotyping was performed against somatic antigen on 18 strains capsular types of which were identified as described above 9(50％), 3(16.7％) and 4(22.2％) strains belong to 1:A, 3:A and 2:D, respectively, but untypable 2 strains(11.1％) were observed. 4. Antibiotic susceptibility test by employing disc method for 24 kinds of drugs revealed that 15 kinds of antibiotics were sensitive to 18 strains of P. multocida isolated such as ampicillin(l00％), penicillin(100％), cloxacillin(56％), piperacillin(70％), cefotaxime(30%), minocycline(60％), chloramphenicol(95％), erythromycin(39％), kanamycin(17％), gentamicin(70%), amikasin(30%), colistin(78％) and nalidixic acid(5％), respectively, but resistant to 9 kinds of antibiotics such as sulpenicillin, cefazolin, cephalothin, cefametazol, cefoperazone, kitasamycin, oleandomycin. lincomycin and bacitracin. 5. Pathological features of 60 cases of swine lungs indicated that pneumonic .lesions were observed in 38 cases(63.3％) examined by macroscopic finding, in which lesions of 8 cases(13.4％) would correspond to those of mycoplasmal infection, and 30 cases(50％) were similar to viral infection by histopathological finding, whereas 22 cases(36.7％) were considered to be normal by ecropsy or histopathological finding.