The article deals with the territorial expansion of mafiatype organized groups. First, the authors argue that mafia expansion is a complex phenomenon, that develops on the basis of a variety of interconnected mechanisms, that refer to both agency and context factors. They move then to illustrate the results of a case study on the Valle d'Aosta Region. On the basis of judicial and documentary sources as well as semi-structured interviews, the study provides empirical evidence on a case of attempted extortion and infiltration by actors linked to 'Ndrangheta groups in a competitive bidding. The results of this exploratory investigation suggest that context factors - such as widespread corruption and illegality, high public expenditure, the overlapping of political and economic élites - can provide excellent opportunities to mafia-type groups that are interested in expanding the territorial range of their business activities.