Book excerpt: Design Models for Hierarchical Organizations: Computation, Information, and Decentralization provides state-of-the-art research on organizational design models, and in particular on mathematical models. Each chapter views the organization as an information processing entity. Thus, mathematical models are used to examine information flow and decision procedures, which in turn, form the basis for evaluating organization designs. Each chapters stands alone as a contribution to organization design and the modeling approach to design. Moreover, the chapters fit together and that totality gives us a good understanding of where we are with this approach to organizational design issues and where we should focus our research efforts in the future.