The paper uses object based models to capture and make visible the system level coordination structure of complex projects. These models facilitate the development of a shared view necessary for effective project management. In the paper, development and use of the models are illustrated using examples drawn from the design of custom silicon. We examine three custom silicon design projects to identify the significant coordination problems encountered as well as the difficulties of using activity based project management tools. Then we develop object based models of coordination structure as a tool to overcome these difficulties. We use these models to capture a project manager's view of the four stages of the custom silicon design cycle: design definition, chip design, prototype manufacture, and system integration. We conclude by discussing the relationship between the coordination structure approach and other project management tools, and the managerial advantages of the proposed approach in the management of projects. Because of their simplicity and stability, coordination structure models form a useful front-end for conventional activity based project management. The approach has particular value for the management of projects in which the task structure is complex, uncertain and unstable, as is typically the case in new product development.