"The role of town planning in British local government is changing rapidly. The most recent development is for planners to offer neither detailed prescription nor abstract goals but various forms of guidance. To evaluate this approach requires an understanding of the ways in which such published suggestions for action are understood or interpreted, and then adopted, modified or rejected, by those to whom they are addressed. This is particularly problematic where the guidance encourages the adoption of novel ideas and the abandonment of traditional approaches. The paper applies the theory of innovation-diffusion to this problem, arguing that addressing novel urban design criteria in an evolving design control system should be thought of as an interactive social process similar to those involved in the spread of technological innovations. The developers and designers who refer to newly defined guidelines in the specification of their projects, and their attempts to gain approval for them, are influenced by the activites of "gatekeepers" and critics of various kinds. They fall into a number of categories as to the speed with which they "adopt" the ideas, and they are more or less sensitive to "barriers" to the pursuit of their versions of the proposed solution-types. As a result, some innovative concepts of urban design "survive" and others are rejected. The paper takes as a example the trend for encouraging developers to consider sustainability in neighbourhood scale design and includes a detailed case study from Manchester. Ill this a description of the Hulme Regeneration project and its design guide is supplemented by discussion of a small set of interviews with members of the team who wrote the guide and are attempting to implement its provisions."