In the study of cancer of domestic animals the skin and its related tissues constitute a preferential site for tumors. In this amply illustrated article are presented for comparison for the most important primary tumors and certain facts concerning secondary or metastatic tumors and tumor-like lesions. Primary tumors are approached by distinguishing between : tumors of the superficial epithelium basal cell and adnexal gland tumors, dermal and subcutaneous tumors, tumors of melanin-producing cells and hemolymphopoietic tumors.