1. ABSTRACT This paper presents a new support system of setting boundary conditions for individual stress analyses. The individual modeling has become a significant technique in computational biomechanics. However, implementation of the stress analyses requires a lot of time because of difficulty in setting the boundary conditions. We discuss necessary functions for speedy individual simulations and develop the support system that satisfies the functions. The realized functions are as follows; selection of nodal points on muscular attachment sites, dispersion of the muscular forces, setting of the direction of the muscular forces and calculation of the reaction forces around a joint portion. This paper also discusses estimation of muscular forces on the viewpoint of effective setting of boundary conditions. Three kinds of objective functions are provided and evaluated by comparison of the computed stress distributions. The developed system is applied to the human mandible for the validity of the performance. Individual modeling is a significant technique for examination of biomechanical characteristics of living bodies. Several research groups including us have proposed the modeling methods to generate finite element models of bones. As the modeling methods serve noninvasively accurate models for computer simulations, it will greatly contribute to clinical diagnosis or medical treatment in the near future. For the contribution to the clinical fields, it is critical to shorten the required time for individual simulations. Figure 1 shows procedures for performing an individual stress analysis of a bone. Among the procedures, automated modeling is an important function to shorten the required time. The authors proposed automated modeling method by use of Delaunay triangulation, which requires a little working time. However, there are still two factors to be discussed for quick individual simulations. One is the function to set up boundary conditions to the FE model for stress analyses. In the musculoskeletal system, nodal points corresponding to restricted portions are fixed and those corresponding to muscular sites sustain distributed forces. General purposed software tools called pre-post processors have such a function of setting boundary conditions. However, these ready-made tools are not suite for analyses of bones and it usually takes a lot of time to set up the conditions. To solve the problem, we make conceptual design of the new system and propose the concrete functions that easily set up boundary conditions for biomechanical analyses. The details are described in the chapter 3.