Objective: The aim of this study was to evaluate the mechanical stresses over the bone and hardware after sagittal split ramus osteotomy (SSRO) fixed with standard titanium or locking plate/screws using finite element analysis. Study design: A 3-dimensional finite element model of the mandible was created, and SSRO and 5 mm advancement was simulated on a computer model. The model was fixed with either 2.0-mm titanium conventional miniplate/screw or 2.0-mm titanium locking miniplate/screw system, and oblique 200 N bite force was applied. Results: The values of von Mises stresses in the cortical layer of the distal segment using the locking plate system was higher. However, in the cortical layer of the proximal segment the stresses were higher at conventional plate system. In the spongiosa layers of both segments, stresses were higher with the conventional plate system. Conclusion: The locking miniplate/screw system spreads the load over the plate and screws and diminishes the amount of force transfered to each unit. © 2009 Mosby, Inc. All rights reserved.