1. ABSTRACTSimulation of mutlibody systems (MBS) that are suitable for the design of their controls require fast processing and access to advanced computational analysis tools. The approach that some MBS simulation programs take is to supply FORTRAN subroutines that represent simple transfer functions. The approach of other programs is to derive the state space description of the MBS and write it in a disc file that can be used by specialized control systems design programs. Both approaches limit the interactive process necessary for the efficient design of control systems. This paper describes a structured and modular multiport approach to the computer-aided simulation of multibody systems. The approach presented in this paper produces models of multibody systems that are not only suitable for the interactive design and evaluation of control strategies, but also suitable for processing on parallel computers.