After the United States-Mexico border, the second longest border between a poor and an affluent region is the eastern external boundary of the European U nion.l This essay discusses the selective permeability of this border, drawing on a larger study of the emergence of a new border regime between Poland and Ukraine following the 2004 expansion of the European Union. In 2005-2006 I conducted twelve months months of field research in Poland and Ukraine, among border guards and immigration officials as well as in migrant communities and civil society organizations. As a participantobserver of cross-border human traffic, I gathered vernacular accounts of crossing, policing, and subverting the border. I relied on historical sources, legal acts, policy handbooks, official statements, and independent reports to situate the accounts I collected within the larger context of "building Europe" east of the former Iron Curtain.