Dental pulp, Microvasculature, Tooth development, Dentinogenesis, Vascular cast Summary: The developmental changes of the vascular supply in the dental pulp were studied in molars of rats from the 19-day embryo to 21 days after birth employing the vascular casting/scanning electron microscope method. In the 19-day embryo, terminal pulpal capillaries were observed in the inner region of the dental papilla and formed a coarse, flattened vascular network consisting of thick capillaries. With the beginning of dentinogenesis, the terminal pulpal capillaries invaded into the odontoblastic layer forming hairpin-like loops and narrowing their lumina. At 21 days after birth, they formed a dense, flattened vascular network consisting of thin capillaries between the odontoblasts, only about 5 μm from the predentin. These findings indicate that the terminal pulpal capillaries play an active role in dentin formation. © 1988, Editorial Board of Okajimas Folia Anatomica Japonica. All rights reserved.