This paper identifies some issues to build a research agenda on the effects of transnationalization and economic development among Mercosur countries. The first section discusses an analytical framework for the understanding of the relation between Foreign Direct Investment (FDI) and the balance of payments constraints to growth in developing countries, assuming that different "types of FDI" may affect such constraints in opposite directions, according to alternative theories. Section II contains a historical perspective of transnationalization in these countries, using a long-run FDI series analysis and resuming some characteristics of the last period. Finally, in the third section, some preliminary conclusions are outlined, attempting to meet the analytical framework and the empirical stylized facts, which allow to identify some issues or topics for such a research agenda.