The contributions in this issue evolved out of discussion papers commissioned by the Department of Public Safety Canada in 2010 for the 12th National and 15th International Metropolis conferences, and cover a wide variety of economic, social, and law enforcement issues related to the mobility of criminal groups. In this introductory article, the authors provide the general background and context for the collection, as well as a brief overview of each of the four papers. It is our hope that this special issue will inspire further rigorous research on this important topic, as well as help contribute toward the development of effective strategies for preventing the spread of organized crime. (Published Abstract)