Lungs from 109 slaughter pigs with gross lesions indicating enzootic Pneumonia of pigs(EPP) and 16 grossly normal lungs, all originating from seven different herds, were subjected to microbiological examinations. The microbiological studies were included both bacterial and mycoplasmal culture. From lungs of 125 slaughter pigs, 87.2% pigs were pneumonia lesions alone or complexly. Mycoplasma spp., pasteurella multocida (P. multocida), Streptococcus spp., and Actinobacillus pleuropneumoniae(A. pleuropneumoniae) were detected in 39.4%, 42.2%, 13.8%, and 3.7% of the pneumonic lungs, respectively. P. multocida was the most frequently isolated organism in pneumonic lungs. Mycoplasmas not isolated organism in 33.9% the pneumonic lungs even if there are gross lessions mycoplasmas. The amounts of pneumonia in lungs with Mycoplasma spp. alone, a concurrence of Mvcoplasma spp. and P. multocida, P. multocida alone, a concurrence of P. multocida and A. pleuropneumoniae, and a concurrence of Mycoplasma spp. and A. pleuropneumoniae were 10.1%, 22.7%, 18.7%, 25%, and 30%, respectively. These findings indicated that P. multocida might be involved in the pathogenesis of pneumonia in slaughter pigs. Mycoplasma spp. was also, in this study, associated with higher frequency of pneumonia. The frequency of pigs snout lesion grade 0~5 inclusive were 27.2%, 28%, 19.2%, 16%, 6.4%, and 3.2% from 125 slaughter pigs. 32(25.6%) pigs were positive and 13~30% in the pigs from seven herds were found to be infected with atrophic rhintis(AR). A total of 46 P. multocida strains in pneumonic lungs were further characterized by capsular serotyping and testing for production of dermonecrotic toxin. 42(91.3%) of strains were capsular A and 4(8.7%) were type D. Out of the type A and type D strains, 86% and 75% were toxigenic, respectively.