Europeanization is an example of initial bargains between states leading to ongoing political adjustment within the states. In this article I apply the concept to NAFTA and look at two of its member states, finding that despite the low level of institutionalization, NAFTA has set in motion new forms of political organization and behaviour, and new demands for political action. This is especially marked in Mexico, and in certain sectors. It is also clearly visible in the changing patterns of cross-border bureaucratic communication. The main conclusions are that: (1) even in a lightly institutionalized regional trade agreement, the institutional, legal and civil society capacity of less-developed members is strengthened; (2) despite the absence of a formal process of policy or institutional development and the lack of legislative instruments, NAFTA has begun a hidden process of domestic adjustment in technical and specialized areas; and (3) like the EU, pressures to expand and strengthen NAFTA have emerged as a result of the initial agreement as well as extraneous factors. These conclusions may offer lessons to the study and practice of regional organizations elsewhere.