North American relations have undergone profound changes over the last 15 years. NAFTA not only created the biggest trading bloc in the world; it was also a catalyst in the conceptualization of the continent as an integrated region. Whereas, prior to 9/11 relations remained primarily at the economic level, the attacks on the U.S. unleashed a new dynamic in North American relations that has seen a significant increase in cooperation in a large number of areas, including security. It remains to be seen whether a new security perimeter encompassing the three countries will emerge. But momentum toward greater collaboration and further integration appears to be afoot. Because of the enormous economic dependence on their mutual neighbour, both Canada and Mexico will need to cooperate with the U .S. on security matters given its importance since 9/11. Ongoing analysis of the evolution of security relations in North America and the impact on Mexico and Canada will therefore not only be likely to continue, but will be necessary. This book aims to contribute to this endeavour.