This volume is the fourth in a series stimulated by the work of the BEQUEST Network, an international discussion group originally funded by the European Commission. The relationship of this volume to the trajectory defined by BEQUEST was set out in the Preface, as was a summary of the contents and findings of the first three volumes. This volume is focused on discussion of the ‘sustainability transition’ in the development of built environment, introducing and reporting on research findings from a number of studies of professional practice concerned with Sustainable Urban Development.