Foreign-born entrepreneurs in Silicon Valley are becoming agents of global economic change, and their increased mobility is fueling the emergence of entrepreneurial networks in distant locations. In this report, AnnaLee Saxenian investigates this development by drawing on the first large-scale survey of foreign-born professionals in Silicon Valley. Focusing on first-generation Indian and Chinese immigrants, the report compares their participation in local and global networks both to one another and to that of native-born professionals. The results indicate that local institutions and social networks within ethnic communities are more important than national or individual characteristics in explaining entrepreneurial behavior. The report also suggests that the so-called brain drain from India and China has been transformed into a more complex, two-way process of “brain circulation” linking Silicon Valley to urban centers in those countries.