This study was performed to evaluate the effects of preoperative and postoperative radiation on the healing of surgical wound and the relationship between surgery-radiation interaval histopathologically. Experimental animals were 64 rats of Sprague-Dawely strain weighing about 180grams. In postoperative radiation group, a single dose of 1000 rads irradiation was delivered on 1,2,3, weeks after incision and 24 animals were sacrificed on the 1st, 3rd, 7th, and 14th day after radiation. In preoperative radiation group incision was performed on 1,2,3,4 weeks after a single dose of 1000 rads and 32 animals were sacrificed on the 1st, 3rd, 7th, and 14th after incision. Tissue specimens were prepared as usual methods and stained with hematoxyline-eosin for ordinary light microscopy. Histopathologic study revealed the following favorable results : 1. In 2 and 3 weeks radiation group after incision, the healing process was unaffected by radiation. 2. In 1 week radiation group after incision, the healing process was slightly retarded, as compared with 2,3 weeks radiation group after incision. 3. In 1,2 and 3 weeks incision group after radiation, the healing process appeared about 7 days later than that of control group. 4. In 4 weeks incision after radiation, the healing process was unaffected by radiation.