Electron microscopic studies were made in 11 cases of benign epithelial tumors (common warts, seborrheic warts, and papilloma) and malignant ones (Bowen’ disease and basal cell epithelioma). Characteristic tubular inclusions were detected chiefly in the cytoplasm of vascular endothelial cells in 6 cases (common warts, papilloma, Bowen’s disease, and basal cell epithelioma). Morphologically, they resembled paramyxoviruses and were exactly similar to those described in collagen diseases, chiefly in lupus erythematosus.