Computer integrated design systems will require an improved understanding of the engineering design process, including formalized notions of (1) the structure of the process, (2) the design tasks that need to be performed, and (3) the information required to carry out these tasks. To help formalize the design process, certain conceptual tools are needed, including an organizational model for the process. This paper outlines such a model for structural engineering design, termed the Multilevel Selection-Development model, which is based on a decomposition of design problems into selection and development subproblems. A few basic concepts involved in the engineering design process are reviewed, and the proposed model is outlined. The application of the model to a simple example is presented, and management of the interactions between subproblems is discussed.