The expression of bone morphogenetic protein (BMP)-2 mRNA and distribution of the BMP-2 protein were studied in dental extraction wounds in mice and the possible role of BMP in the generation of bone structures was discussed. Histologically, new bone formation started 3 days after dental extraction in the wounds of mice and continued for 7 days. Immunohistochemically, a polyclonal antibody against recombinant BMP was used. BMP-2 was expressed in the osteoblasts and mesenchymal cells 3 days after extraction and was present for 7 days. Using in situ hybridization 1 and 3 days agter extraction, however, high BMP-2 mRNA levels were present in osteoblasts and mesenchymal progenitor cells of bone marrow adjacent to the wounds and a weak BMP-2 mRNA expression persisted in osteoblasts of the alveolus. Five and seven days after extraction, BMP-2 mRNA was expressed intensely in the osteoblasts around the new bone tissues. Fourteen days after extraction, only a few osteoblasts on the trabecular showed a low level of BMP-2 mRNA expression. These results suggest that BMP-2 plays an important role in the extraction wound healing process, such as bone formation and apposition.