Chemotherapy is applied in the treatment of malignant disease to decrease the number of malignant cells, and to avoid damage of the living tissue and growing cells which must be reduced to the lowest level. In the combination of cytostatics Vincristine, a Vinca-alkaloid, is widely used. The purpose of this study was to analyse the pulp and dentine in experimental animals after the administration of Vincristine. Wistar rats of both sexes were used. Vincristine (Onkovin, Lilly) was injected in the neck skin fold on the 7th and the 8th postnatal day in a single dose of 0.1 mg/kg b.w. At the 24th postnatal day experimental and control animals were sacrificed. Both jaws with teeth were prepared for routine histologic examination. The results showed that Vincristine effect was different in different regions of the tooth. The number and disposition of odontoblasts was reduced in all areas of tooth sections, especially in the pulp horn. In the central part of coronal and radicular pulp tissue blood vessels were dilated and filled with blood cells. A histologic appearance of newly formed dentine was irregular.