This chapter examines trends in Latin American economic performance and Latin American economic policy during and immediately after the Second World War. The emphasis is principally on the interaction of the Latin American economies with the international economy. In the 1930s, as the previous chapter has shown, Latin American economic performance as a whole was still driven by the export of primary products, although in most countries industry grew faster than real gross domestic product (GDP). Economic policy achieved the unusual feat of stimulating primary exports and industrial development at the same time. This was an important achievement, since primary exports were the main source of foreign exchange for the import of intermediate and capital goods. By the 1950s, however, Latin America was deeply entrenched in import-substituting industrialization (ISI). Its key characteristics were a strong discrimination against exports combined with an increased need for foreign exchange. Thus it discriminated against the sector which was crucial to its functioning. We need to understand, therefore, how and why policy evolved from the relative consistency of the 1930s to the contradictions of the 1950s. This chapter will explore first, the impact of the Second World War on the Latin American economies, and second, the evolution of economic policies – and economic performance – in the immediate aftermath of the war. The analysis will necessarily have to touch on the 1950s, since our conclusion is that the explicit rejection of the old export-led growth model and the consolidation of the new inward-looking ISI model of economic growth and development occurred, in the larger countries at least, between the late forties and the middle of the following decade.