Two 2 and 7 months-old holstin and one 3 months-old native Korean calf suffering from respiratory illness were submitted to the National Veterinary Research Institute for euthanasia and pathologic examination. At necropsy diffuse lobar pneumonia was present in apical cardiac and diaphragmatic lobes in all calves. Microscopically acute multifocal bronchiolitis and interstitial syncytial cell formation were frequently observed. in addition occlusion of bronchiolar lumen due to cellular proliferation and fibrosis accompanied by interlobular septal emphysema were also present. Immunohistochemically bovine respiratory syncytial virus antigen were positively identified in lung lesions including bronchial and bronchiolar epithelium alveolar macrophages and lymphocytes.