Empirical evidence suggests that the emergence of international production networks in East Asia results from market-driven forces such as vertical specialization and higher production costs in the home countries and institutional-led reasons such as free trade agreements. This paper examines two industries — autos and auto parts, and hard disk drives (HDDs) — to understand international production networks. The study examines the structure of vertical intra-industry trade among East Asian countries, especially members of the Association of Southeast Asian Nations, depicts international production sharing in the selected industries, namely HDD, and automobiles and automotive parts, in the region. The study also points out the importance of the People’s Republic of China and Thailand as assembly bases. It concludes that investment promotion policies contributed more to the emergence of international production networks than free trade agreements.