This Guide is aimed primarily at the enterprise architect undertaking the design of an information infrastructure to support internal and external user-based collaboration and commerce. This infrastructure may comprise Commercial Off-the-Shelf (COTS) products and existing IT assets. It addresses the key issues that an enterprise architect needs to consider in the process of developing an enterprise identity management architecture, and discusses practical aspects which influence decision-making during that process. It focuses on the business perspective, but also includes consideration of individual, social, governmental, and economic perspectives. We believe it represents today's common practice on the essential activities of architecture design and deployment as applied to architecting Identity Management infrastructures, and hope architecture practitioners will find it useful as a guide to steering an effective course to the delivery of demonstrable and measurable business benefit.