IN THIS brief survey, the biologic characteristics of the principal malignant epithelial neoplasms of the skin will be presented from the point of view of gross morphology and its importance in diagnosis, prognosis and treatment. Melanomas will be excluded, and the group to be considered will consist of basal cell and squamous cell epitheliomas, including Bowen's disease, and carcinomas of sweat and sebaceous glands. An idea of the relative frequency of these tumors may be gained when it is stated that during a ten year period there were recorded in the laboratory 1,224 malignant tumors of the skin—605 of these were basal cell cancers; 309 were squamous cell tumors, including Bowen's disease; 21 were sweat gland carcinomas, and 2 were sebaceous gland cancers. The remainder consisted of 150 malignant melanomas, 55 sarcomas and 82 secondary neoplasms. In order to obtain a broad general view of cancer, one should visualize it