Histopathologic examination was performed on 14 Japanese serows having a number of papular lesions on the oro-nasal mucosa and on the skin. They were obtained in Tohoku distict from 1979 to 1982, and died from weakness or pneumonia. In the mucosal and cutaneous lesions, vacuolar or reticular degeneration of the prickle cells with basophilic or eosinophilic cytoplasmic inclusions followed initial focal acanthosis. Epithelial or epidermal necrosis and scabs were observed in the prolonged lesions. There were marked hyperemia, hemorrhage, capillarization and proliferation of histiocytic Cells in the mucosal propria or dermis, infrequently accompanying pustular or hyperkeratotic lesions. The mucosal and cutaneous lesions classified into 3 groups; (1) papular necrotic stomatitis or dermatitis, (2) pustular necrotic stomatitis or dermatitis, and (3) papular necrotic dermatitis with marked hyperkeratosis, due to histopathologic criteria.