Summary In this study, we investigated the clinical, cytological and haemotological changes in after weekly vincristine sulphate administration in naturally occured a four year old male dog referred to Kırıkkale Univercity Clinics of Veterinary Faculty with history of haematuri. Physical examination revealed cauliflower like appereance, 8 cm diameter haemorrhagical mass on bulbus penis. The diagnosis of TVT was established on the basis of cytologic results and clinical symptom. Treatment was considered of intravenous 0.025 mg/kg vincristine sulphate in 500 ml saline solution. The treatment was conducted one a week for a duration of six week. In this case, it was aimed to show that cytological examinations in a male dog with TVT is required for definite diagnosis and alteration of blood parameters during treatment with appropriate doses of vincristine sulphate.