Successive changes in the vascular pattern during the osseous healing of extraction wounds were investigated by studying microvascular casts under a scanning electron microscope. The casts were prepared utilizing the plastic injection method, after the extraction of the upper four incisors of the Japanese monkey (Macaca fuscata). Five days after extraction, vascular buds have sprouted from a pre-existing blood vessel on the alveolar wall into the blood clot, and leakage of the plastic injected was found from the tips of these buds. One week after extraction, newly-formed vessels have extended widely to the socket center, and dilated vessels have arborized towards the socket opening. Two weeks after extraction, the socket was filled with thick, newly-formed vessels. In the socket fundus, the woven bone was formed between irregular vascular networks, but was arranged different in the socket wall. Four weeks after extraction, the new bone forming on the socket wall became thickened and converted to a lamella-like bone. Inside it the woven bone was raised from the fundus, and blood vessels leaving it were decreased in their thickness and passed toward the socket center. Five weeks after extraction, the new bone structures came up to the level of the socket opening, the surface of which appeared as a shallow concavity (pivot), from which vascular bundles were directed to the socket opening. A beginning of the bone-remodeling was seen in osseous trabeculae in the socket fundus. Six weeks after extraction, almost all of the socket became filled with new trabeculae, between which, fine vascular networks were sorted out and communicated with the periosteal vascular network beyond the socket margin. The interalveolar septum between the extraction sockets was thickened by deposition of the lamella-like bone to be remodeled to a cancellous bone. It can be said that microvascular patterns formed through all stages of the osseous healing of the extraction wounds contributed to a woven bone formation and its development.