Transmissible Venereal Tumor (TVT) is one of the most uncontrolled spreading tumor via mating between dogs observed in both sexes. The clinical findings are less remarkable and are usually located in the caudal part of the penis and may include preputial discharge, licking of the region, dysuria, phimosis or paraphimosis (occasionally). In this study, the incidence of TVT and the relations of tumor with some factors were investigated in 145 male dogs, in Eskiºehir, Turkey. TVT’s diagnosis was based on location of the tumor mass and mainly exfoliative cytological findings. Smears of caudal part of the penis were painted with Giemsa staining method. The cells in the smears were identified as typical transmissible venereal tumor cells, polymorphnuclear leukocytes (PMN), erythrocyte, parabasal, intermediate, nucleated and anuclear superficial cells. In exfoliative cytological examinations, TVT cells were observed in the smears of 17 dogs (11,72 %), but only four of them (2,76 %) had TVT lesions clinically. Thirteen (8,97 %) of dogs had TVT cells but not having TVT lesions . It was found that the ages, weights and breeds of dogs had no effect on the TVT lesions and TVT cells. TVT positive animals were determined to have more erythrocyte and intermediate density than negatives and no association with other cells were found. PMNs were significantly different and high in the TVT cell positive cases compared to the negatives. In dogs with negative TVT cells, parabasal, intermediate, nuclear/anuclear superficial cells were more than those positives. As a result, the male dogs having no lesions could be infected with TVT. Dogs should be examined not only clinically, but also cytologically, to determine whether TVT cells are present. This method can be an easy way to find and treat TVT lesion-free but infected dogs at an early time.