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 genera] models for the design process. However, it has been shown that these models are rarely used by engineers in practice. This dissertation advances the concept that useful design models must include methodologies that are particular to a given field or type of design. The inclusion of these knowledge-domain-dependent methodologies provides a complete framework for the greatest utility to the designer. This dissertation describes a general approach to engineering design and proposes a model for developing design assistance tools useful to the practicing designer. The methodology and the model are applied to the domain of cam mechanism design. The model describes the conceptual design process that begins with formulating objectives and establishing specifications and concludes with the actual synthesis of the cam profile. The design model is then incorporated into a comprehensive modular computer tool that is integrated with a PC-based CAD package. This dissertation contributes to both the field of engineering design and cam mechanism design. It provides a design model that incorporates a detailed methodology with information and analytical tools for design. By focusing on the knowledge domain of cam mechanism design it contributes to this field as well. Most prior research focused on techniques for synthesizing the cam profile and provided little assistance for the earlier stages of design. No previous tools have been developed that provide the scope of assistance presented in this dissertation. / Ph. D.