Regional integration has been an objective, at least formally, within Latin America and the Caribbean (LAC) almost since Independence in the nineteenth century. Contemporary schemes for LAC integration, however, rooted in economic cooperation as a means to industrial development, date from the 1960s. Brazilian participation, in view of the size of the economy and its position as sub-regional power, was vital for the success of these initiatives. But Brazil was not fully committed to integration in the 1960s, thus weakening the drive for hemispheric economic cooperation. Yet in the 1990s Brazil endorsed a new and imaginative attempt at integration, the Common Market of the South (MERCOSUR). This chapter will explain Brazil’s new enthusiasm for region-building in terms of its changing position within the global economy and as a consequence of changes within the state. The transformation of Brazilian policy towards the rest of LAC was partly the result of state elites’ altered perspectives on national political interests, alongside pressures to adjust the economy to the terms of an increasingly open but regionalizing world economy. Understanding the nature of the state is therefore central to understanding Brazilian regionalist policy. The second part of the chapter will analyse what state elites hope to gain from membership of MERCOSUR.