Diazepam, 10 mg., was given intravenously to fifty-one patients, and 75 mg. meperidine plus 25 mg. promethazine was given intramuscularly to forty-eight patients undergoing oral surgical procedures under local anesthesia. Over-all sedation was noted as poor in 15 per cent of the patients in the meperidine-promethazine group and in 6 per cent in the diazepam group. It was fair in 17 and 24 per cent, respectively. The excellent or good ratings were about equal, that is, 68 and 70 per cent, respectively. On diazepam, 12 per cent of the patients were rated as “awake-drowsy,” as compared with 16 and 84 per cent, respectively, on meperidine-promethazine. Characteristically, however, the patients given diazepam fell into a light sleep during the operative procedure but could easily be aroused when spoken to. Cooperation was rated as excellent or good in 94 per cent of the patients given diazepam and in 67 per cent of those given meperidine-promethazine. Other clinical manifestations, such as relaxation and ease of induction or apprehension, restlessness, and anxiousness, were similarly distributed in the two groups. The sedative effect of diazepam appeared minutes after the injection and disappeared completely at the end of 40 minutes, whereas that of meperidine-promethazine usually lasted for 1½ hours following the operation. In patients undergoing operative procedures lasting longer than 40 minutes, a small additional dose of diazepam would presumably have completely eliminated residual restlessness and anxiety. Meperidine-promethazine produced dry mouth, dizziness, and nausea. Except for euphoria in three patients, no side effects were noted with diazepam. Intravenous diazepam was found to be a very satisfactory premedication for patients undergoing oral surgical procedures under local anesthesia.