A Dalmatian female presented with a history of vaginal bleeding and was diagnosed as having transmissible venereal tumour (TVT) after cytological examination of the vaginal growth revealed typical TVT cells. A cytology of the aspirate from multiple nodules in the skin near the abdominal and inguinal pair of mammary glands revealed similar cells suggestive of metastasis to skin of mammary region. Chemotherapy was initiated with weekly injections of vincristine sulphate (0.025 mg/kg BW, IV, SID) and haematological examination was performed pre- and post-treatment to assess the prognosis of the patient and side effects of the drug. The major side effects observed during the course of the treatment were high body temperature, mild neutropaenia and significant decrease in packed cell volume, haemoglobin, total leucocyte and erythrocyte count. Four weekly injections of vincristine were administered, and 4 weeks from initiation of treatment, the tumour and nodules were gone, suggesting complete recovery.