Implementing the lean principles and tools in manufacturing has been successful in many companies. This success has led to different implementations, of these principles, in other organizational activities such as design and management. While these implementations can produce some improvements, the segmentation of the product development processes in most company limits the potential for achieving the desired goals and in some cases the success of the implementation process itself. In other words, full success of lean principles implementation cannot be achieved when applied to isolated segments of the product development process. This paper addresses lean design, in the context of a fully integrated product realization process. The paper discusses the integrated nature of any product realization process and its flow from concept to production. It also addresses the effect of this integrated nature of the process on the implementation of the different lean principles such as value, value streaming, flow, pull, and perfection.