By critically appraising current theories of both Foreign Direct Investment (FDI) and agglomeration, this book explores the variety of links that exist between these two externality-creating phenomena. Using in-depth empirical research on Mexico, Jacob Jordaan constructs and analyzes several datasets on Mexican manufacturing industries at various geographical scales, creating innovative models on FDI externalities that incorporate explicitly regional considerations. The empirical findings identify both direct FDI spillover effects as well as the effects of agglomeration on these externalities. In extension of this, the analysis also contains analysis of FDI productivity effects that arise through inter-firm linkages between FDI and local Mexican suppliers.