Good engineering practice requires designers to incorporate knowledge, processes and skills to produce a superior product. Each stage of the product realization process requires that the designer utilize available resources to make sound engineering decisions in a timely manner. Much of the research on engineering design has focused on formulating general models for the design process. However, it has been shown that these models are rarely used by engineers in practice. This paper advances the concept that useful design models and the resulting support systems must include methodologies that are particular to a given field or type of design in an overall design methodology framework. The inclusion of these knowledge-domain-dependent methodologies provides a complete framework for the greatest utility to the designer. The paper then describes a decision support system, AutoCam, that embodies these principles for assisting designers in the process of synthesizing cam mechanisms. AutoCam is a comprehensive, modular computer tool that is integrated with a PC-based CAD package to assist the designer throughout the design process, from the problem confrontation, through the formulation of objectives and establishing specifications, and synthesizing the resulting cam profile. While several software programs are available for synthesizing a cam profile from a given motion program, no other current package assists the designer with the complete process of cam mechanism design. AutoCam provides a design model that incorporates a detailed methodology with background information and analytical tools for design.