The Ministry of Sustainable Development, Environment and Parks of Québec (Ministère du Développement durable, de l'Environnement et des Parcs du Québec-MDDEP) held a 3-d provincial nuclear emergency response exercise in September 2008 that saw participation from Canadian provincial and federal departments. Nuclear emergency exercises are regularly held in Québec, given the presence of the Gentilly-2 nuclear power plant situated in Bécancour on the St. Lawrence River. The significance of this exercise is that it marks the first exercise held in Canada where environmental samples spiked with relevant radioisotopes were analyzed during the exercise, both on-site and remotely, and where the results of those analyses had a direct impact on the decisions made during the exercise. Following the exercise, samples were sent to two other laboratories that are part of the Canadian National Nuclear Laboratory Network for analysis, providing the first intercomparison exercise for the Network. The results of the analysis of the air and drinking water samples, as well as the lessons learned during the exercise, are presented and discussed in this article.