This paper discusses four aspects of computer modeling of restraint system performance: Components of restraint systems (both vehicle and restraint hardware components) Analytical representations of the system including lumped mass occupant computer codes (CAL3D, MADYMO, etc.) as well as finite element codes (PISCES™, PAM-CRASH™) Design applications of restraint system computer models Relations between auto makers and restraint system suppliers. To begin the discussion, the physical parameters of vehicles and restraint systems that affect occupant protection are listed. The purpose is to illustrate the difficulty in separating vehicle components from restraint system components. This is followed by a review of the current software for occupant simulation. This is complemented with a discussion of current development of finite element and finite difference representations of airbag restraints and occupants. The ability of the various computer procedures to produce realistic results is discussed. The paper is concluded with a section on the relation of auto makers with restraints system suppliers. This emphasizes the strategic interaction required in order to assure that each partner has timely access to a sufficient subset of the other's parameter data for efficiency in the modeling, design, and test cycle.