We examined the feasibility of intraoperative conscious sedation employing patient-controlled analgesia with alfentanil (PCA-alfentanil) in 20 adult outpatients undergoing third molar surgery under local anaesthesia. A loading dose of intravenous alfentanil 15 mg/kg was administered immediately before local anaesthetic administration using 2% lignocaine with 1:80,000 adrenaline. This was followed by a background alfentanil infusion of 0.05 mg/kg/min. On demand alfentanil doses were 4 mg/kg with lockout intervals of 3 minutes. All patients were mildly sedated, easily aroused verbally and co-operative throughout the surgery. None experienced any cardiovascular or respiratory complications related to PCA-alfentanil. Immediate postoperative complications included nausea, vomiting and pruritus. High patient comfort and acceptance scores suggest that the use of PCA-alfentanil can be a useful adjunct to local anaesthesia in adult outpatients undergoing third molar surgery.