1. 1. The effects of antihistamine therapy on the postoperative sequelae of oral surgery were studied on a double-blind basis, using extended-action tablets of brompheniramine maleate (an antihistamine) and identical placebos. The patients included 114 who were operated on for impaction and 34 other surgical patients who underwent odontectomy, apicoectomy, and alveoloplasty. 2. 2. Among patients who were operated on for impaction, postoperative edema and trismus were significantly less in those who received the active medication than in similar patients who received the placebo. 3. 3. Among patients operated on for other conditions, those who received the active medication did not develop markedly less edema and trismus than did those who received the placebo. 4. 4. The edema and trismus that developed in patients who received the antihistamine were resolved more rapidly and the patients returned to control levels more rapidly than did patients receiving placebo.