AUTOSIM: A computer language for representing multibody systems in symbolic form to automatically formulate efficient. Object-oriented symbolic computation methods are developed in this paper for describing and analyzing multibody systems, particularly vehicles. Computer data objects are defined for symbolically representing (1) vector/dyadic algebraic expressions, (2) physical components in a multibody system, and (3) program structures needed in a simulation code. With more powerful symbolic manipulation capabilities, all techniques normally employed by human analysts and programmers can be mimicked to obtain efficient numerical simulation codes. These include: selecting “natural” coordinates, dropping negligible terms, and introducing intermediate variables to avoid redundant computations. Also, the description of unusual forces and moments is straightforward when the analysis software can deal with general vector notation. The methods are demonstrated for an example three-dimensional vehicle handling model.