The purpose of this study was to examine the effects of radiation on the healing process of tooth extraction wounds. X-ray doses of 10Gy or 20Gy were delivered, once, to the maxillofacial area of Wistar-strain rats. Then, 24 hours after irradiation, the maxillary first molars were extracted bilaterally. The animals were sacrificed 3, 7, 10 14, 21, 42, and 84 days after tooth extraction, and the maxilla were sliced, to make thin sections. These specimens were then double stained with alkaline phosphatase (ALP) and tartrate resistant acid phosphatase (TRAP). The ratio of bone area to socket area (bone formation ratio), the ratio of bone length to ALP positive area length (ALP positive ratio), and the number of TRAPpositive cells, were evaluated. The results showed:(1) The bone formation ratios at days 3 and 7 after tooth extraction were significantly low in both irradiation groups, compared with those for the non-irradiation group. (2) The ALP positive reaction ratio peaked 7 days after in the non-irradiation group. In both irradiation groups, the ratios that were worked out at 3 days and 7 days after were significantly lower than those in the non-irradiation group. (3) There was no significant difference in the number of TRAP-positive cells between the nonirradiation group and the 10Gy irradiation group. In the 20Gy irradiation group, the TRAP-positive cell count plummeted to a significantly low level at 3 days after tooth extraction, compared with that in the non-irradiation group.