Abstract The analgesic efficacy of aceclofenac in the control of pain after surgical extraction of impacted mandibular third molars was compared with its preoperative administration. Two groups of 20 patients each were medicated with 2 tablets of 100 mg aceclofenac taken orally either 1 h before surgery or in the early postoperative period. All surgeries were performed by the same surgeon and the surgical technique was the same for all patients. Pain was assessed with a Visual Analogue Scale and a 0–4 Scale, as well as by counting the number of analgesic drug tablets taken after the surgery. Patients in the preoperative group took fewer tablets postoperatively and had a lower pain score both in the Visual Analogue Scale and the 0–4 Scale. This difference, however, was statistically significant only at 6 h after surgery, which is the time of maximum pain for this surgical procedure. Aceclofenac was more efficient in controlling pain when administered before the surgery.