The roles that illicit and illegal activities have played in urban and regional development and governance are extremely diverse. It has long been recognised within political, legal, criminal justice, media and civic circles that a range of illicit actors and acts have been - and continue to be - part of the processes and institutions of urban and regional governance and development across a diverse, international terrain. It is widely recognised that it is difficult to draw a line among categories such as licit and illicit, legal and illegal, formal and informal within the processes of economies, urban and regional governance and development and their spaces. The threshold between licit and illicit is often not clearly definable. Developing reliable and valid empirical evidence on the extent of the impacts and influence of illicit and illegal behaviours within urban and regional development is beset with difficulties.