Objective: The purpose of this double-blind study was to evaluate the effect of intra-articular opioid injections on postoperative pain and joint mobility after arthrocentesis of the temporomandibular joint (TMJ). Method and Materials: Forty patients suffering from persistent pain in combination with anterior disc displacement (22 with reduction, 18 without reduction) and unresponsive to nonsurgical therapy underwent arthrocentesis of the affected TMJ under local anesthesia. All patients were randomly assigned to 2 groups. In group 1 (20 patients), 1 mL of buprenorphine solution was injected into the joint space at the end of the intervention; in group 2 (20 patients), 1 mL of saline was used. For postoperative pain management, all patients received Paracetamol ad libitum. Preoperatively and at postoperative days 2, 4, 7, and 14, individual pain levels were determined on a visual analogue scale together with maximum mouth opening. Results: At days 2 and 4 after the intervention, remarkable differences were detectable between the 2 groups, showing a rapid normalization of joint mobility and pain scores in group 1; in contrast, improvement in group 2 was delayed. Conclusion: Intra-articular injections of long lasting opioids seem to influence joint mobility and pain positively within the first week after arthrocentesis. Keywords: arthrocentesis, opioids, pain management, temporomandibular joint