From 2,373 slaughtered pigs examined, 1,899 of them had visible evidence of pulmonary lesion. The lungs with pulmonary lesion were examined by grossly, histopathological technique to investigate the prevalence accordint to season, severity ofpulmonary lesion, types of the pneumonia and relationship between rearing management and prevalence of pulmonary lesion. The results were as follows: 1. Prevalence of pneumonia according to season was 72.3 % to 85.9% and the higher prevalence was in winter. 2. In the severity of pulmonary lesion, rates mild, moderate and severe lesions were 38.3%, 47.0% and 14.7%, respectively. Prevalence of mild lesion was the highest in autumn. Prevalence of moderate and severe lesions was the hihgest in winter. 3. In the type of pneumonia, rates of interstitial pneumonia and bronchopneumonia fibrinous pneumonia were 23.6%, 13.0%, and 3.4%, respectively. Prevalence of interstitial pneumonia was high in spring and autumn while that of broncho-pneumonia and fibrinous pneumonia was high in winter and summer, respectively. 4. In relationship of pulmonary lesions according to severityo fpulmonary lesion and types of pneumonia, similarity was observed in prevalence of mild lesion and bronchopneumonia.