In this study, the effects of heparin on dentinal resorption was investigated in rats. Animals were injected with 2 x 2 IU/g Na-Heparin subcutaneously for 33 days. Histopathological examination of the anterior teeth revealed capillary proliferation, congestion, and fibrosis in the pulp in addition to resorptive lacunae and degenerative bone spiculae in the peripheral bone tissue. Development of fibrosis in the pulp tissue was verified by densitometric analysis, which revealed a 30% increase in mean density after heparin administration. No resorption at all, however, was seen in dentin.