The use of chemotherapy is a recent development in veterinary oncology. After presenting the mechanisms of action, their activity on cellular kinetics and the toxicity of the anti-mitotic agents, the author elaborates on the methods of utilization of the 5 drugs most commonly administered in veterinary medicine: cyclophosphamide, vincristine, adriamycin, 5-fluorouracil and cisplatinum. The indications for chemotherapy are taken up in the last section where a distinction is made between curative chemotherapy (primary or adjuvant) and palliative chemotherapy.