Part 1 traces the evolution of control of organized criminality in Montreal. The simultaneous disappearance, during the 1960's, of patronage as a way of governing and of corruption as a crucial element in the operation of criminal practices is seen as a very significant development in this respect. The second part of the paper deals more directly with the study of crime and shows how the analysis of the structure of criminal opportunities and black markets should precede, logically and empirically, the description of the size or complexity of the internal organization of criminal groups. A total of 48 reference notes are included. (Author abstract modified)