Ten randomly selected adults who had undergone orthodontic treatment and isolated mandibular advancement for correction of mandibular deficiency were evaluated clinically and radiographically (mean, 42.8 months postsurgery) for signs and symptoms of masticatory and temporomandibular joint dysfunction. A three-part evaluation of the subjects was performed. This consisted of an anamnestic evaluation, a clinical examination, and a radiographic examination. The anamnestic evaluation (previous medical history) revealed that prior to surgical intervention 20 percent ( 2 10 ) of the patients noted the presence of facial pain which we believed was localized to the masticatory musculature. The pain was reported to have resolved postoperatively. No patients reported the presence of pain in their temporomandibular joints prior to surgical treatment. However, three patients related a history of postoperative facial and joint pain that had not existed preoperatively and had not resolved at the time of follow-up examination. Temporomandibular joint sounds were not reported by any of the patients preoperatively. Immediately after release of intermaxillary fixation, 50 percent ( 5 10 ) of the patients noticed temporomandibular joint sounds. Two of these patients noted a resolution of the joint sounds without treatment, while the remaining three patients reported the presence of joint sounds at the time of re-examination. Further, these were the three patients who had a history of unresolved postoperative facial and joint pain. Clinical examination of the temporomandibular joints at the time of recall evaluated the range of mandibular movements and the presence of joint pain or sounds during function. These examinations revealed that measures of mandibular movements were somewhat below normal. Three patients demonstrated combined ipsilateral joint and masticatory muscle pain during mandibular function, upon contralateral masticatory loading, and in response to palpation. These were the same patients who reported persistent pain and joint sounds during the anamnestic evaluation. Thirty-five percent ( 7 20 ) of the joints demonstrated sounds (popping or crepitation) via auscultation during jaw opening or closing. One joint demonstrated popping during contralateral masticatory loading. Cephalometric laminograms were obtained of each of the twenty joints with the mandible in three positions: maximum intercuspation, mandibular rest position, and maximal opening. Various anatomic measurements were quantitated from these radiographs and three parameters—condylar position, condylar movement, and incidence of arthrosis—were compared to normative data obtained from the literature. All parameters evaluated were compared with those of a group of patients who had undergone superior repositioning of the maxilla. 1 When compared to normal, it was found that persons who had undergone mandibular advancement surgery demonstrated (1) a relatively retropositional location of the condyle within the glenoid fossa and (2) reduced condylar movement during maximal mandibular opening. These joints exhibited a greater incidence of arthrosis when compared to those of normal persons. When compared to the patients who had undergone superior maxillary repositioning, the primary radiographic differences were found to be (1) a greater reduction in condylar movement in the maxillary surgery group and (2) higher incidence of arthrosis in the group of patients who had undergone mandibular advancement surgery. 1 These findings demonstrate the need for more critical prospective clinical and radiographic evaluation of patients prior to surgical-orthodontic correction of mandibular deficiency.