Key sections of the North American Free Trade Agreement (NAFTA) deal with temporary labor mobility. Ideally, NAFTA status provisions should make the temporary movement of professionals easier across the border of all NAFTA countries. However, in the case of some key sectors, it is arguably not the case. Within the context of recent literature on cross-border trade, city regions, regionalism, international labor mobility, and post-September 11 security measures, this book probes the dynamics of transitory immigration of ‘knowledge-workers’ between the North American west coast city regions of Vancouver, Seattle, and the greater San Francisco Bay and Silicon Valley area. This book includes in-depth interviews with Canadian and US immigration officials, immigration attorneys and executives and professional staff of new technology firms and Fortune 500 companies. It ultimately explores whether or not the Canada–US border is an impediment to the development of a cross-border high-tech clusters.