In this paper, the integration infrastructure for a simulation-based design (SBD) environment for mechanical system design developed at Center for Computer-Aided Design at the University of Iowa is presented. The SBD environment comprises the integration infrastructure and workspaces/tools that exploit Computer Aided Design (CAD)/Computer Aided Engineering (CAE) and software engineering technologies in support of design of large scale mechanical systems. The principal functional components of the SBD environment are engineering workspaces and CAD/CAE tools that bring engineers, servicemen, and customers early in the product development process to assess design of the product concurrently. The infrastructure is based on the newly invented engineering views that allow engineers from various disciplines to view the product with their own perspectives. The infrastructure allows engineers to create CAD and simulation models of the mechanical system, access engineering workspaces and CAD/CAE tools to perform multidisciplinary engineering analyses, use planning tools to create and manage simulation processes, communicate and exchange engineering data, and conduct design trade-off analyses and make informed decisions to yield a robust optimum design. The presentation given in this paper assumes that simulation-based design activities are performed in the product detailed design stage. The environment is being extended to support concept design.