Purpose: This study evaluated the efficacy of autologous fat grafting to the temporomandibular joint (TMJ) as an adjunct to prosthetic joint reconstruction in preventing fibrosis and heterotopic bone formation and determined its effects on postoperative joint mobility. Patients and Methods: Fifteen patients (2 male, 13 female) underwent TMJ reconstruction with Techmedica (Techmedica, Inc, Camarillo, CA) custom made total joint prostheses, Seven patients had bilateral and eight had unilateral surgery, for a total of 22 joints, All patients had autologous fat from the abdomen grafted around the articulating portion of the joint prostheses after the fossa and mandibular components had been stabilized. Twenty patients (2 male, 18 female) without fat grafts sewed as controls, There were 17 bilateral and 3 unilateral cases, for a total of 37 joints. These were the last 20 patients with adequate data available for inclusion treated before patients receiving primary fat grafting as part of the joint reconstruction. Results: In the control group, the average preoperative maximum interincisal opening (MIO) was 26.8 mm, and at long-term follow-up it was 33.1 mm. Contralateral excursive movements averaged 3.2 mm preoperatively and 1.7 mm at long-term follow-up. In the fat graft group, average preoperative MIO was 26.9 mm, and at long-term follow-up it was 38.7 mm. Contralateral excursive movements averaged 2.3 mm preoperatively and 2.2 mm at long-term follow-up, The differences in measured function between the two groups were found to be statistically significant (P less than or equal to.01), Although both groups experienced a significant decrease in pain, there was no significant difference noted in the patients' perception of their level of pain at long-term follow-up as expressed on visual analog scale evaluations. There was no radiographic or clinical evidence of heterotopic calcifications or limitation of mobility secondary to fibrosis in any of the experimental groups, whereas seven control patients (35%) exhibited this phenomenon and required reoperation. Conclusions: Autologous fat transplantation appears to be a useful adjunct to prosthetic TMJ reconstruction. Its use appears to minimize the occurrence of excessive joint fibrosis and heterotopic calcification, consequently providing improved range of motion.