Subcontracting is a widespread feature of the industrial landscape: 74% of operators make use of such services. Since less than 10% of accidents involve a subcontractor it would appear that this practice does not represent a high level of risk. And yet the consequences can be severe. Through a series of examples, this dossier, co-written by BARPI and IRSN (Institute for Radiological Protection and Nuclear Safety), depicts the nature of accidents linked with subcontracted activities. By analysing these incidents, we were able to draw up a list of recommendations and good practices, starting with the thorough preparation of the work site and consultation with subcontractors, all the way through controls upon completion of the works.