This study observed the frequency of post-surgical infection according to post-surgical application of antibiotics in order to evaluate the benefits of the use of antibiotics after the orthognathic surgery. 349 patients without any specific medical history were divided into two groups depending on whether or not antibiotics had been applied after the surgery. The mean(SD) age of the 349 patients was 22.7(${pm}4.25$) with a male-female ratio of 168:181. 226 patients received only 1.0g of a third-generation cephalosporin(Cefpiramide) intravenously 30 minutes prior to the surgery. Likewise, 123 patients received 1.0g of Cefpiramide 30 minutes prior to the surgery and twice daily longer than the third day after surgery. The mean(SD) duration of administration was 4.75(${pm}0.89$) day. The patients were evaluated after surgery for any postoperative infections according to the criteria: purulent drainage from a wound, spontaneous wound dehiscence accompanied by swelling, pain, and fever around the wound. However, 14 patients of 226 patients received antibiotics only prior to the surgery developed postoperative infection, 2 patients of 123 patients received antibiotics longer than postoperative 3 days developed postoperative infection. Postoperative infection frequency showed no significant difference between the two groups(p=0.094). Also, bi-maxillary operation and mandibular operation alone, showed no significant difference in the frequency of post-surgical infection when antibiotics had been continuously used after the surgery. From this study, postoperative use of antibiotics seems to be unnecessary with view of the little significance of the factors that could affect the wound infection.