The State Planning System (SPS) is presented in the context of a mathematical model used to generate information about the possible impacts of postsecondary education policy decisions. Section I provides an introduction to modeling in higher education management, identifies some current postsecondary education modeling efforts, offers some criticisms of modeling, and presents suggestions for further development of modeling in postsecondary education planning and management. Section II describes modeling activities in several states and suggest criteria for evaluating the potential usefulness of different modeling approaches. Section III describes the SPS as a modeling tool and relates it to other national and state-level modeling activities. A glossary is included containing terms that are associated with the SPS. (Author/CMV)