In this essay, I review opposite positions on the relationship between migration and the socio-economic development of sending countries and regions and the theoretical schools that underlie each of them. In order to adjudicate between these competing perspectives, it is necessary to distinguish between the human capital composition of different migrant flows, their duration, and their structural significance and change potential. This theoretical discussion culminates into a typology that seeks to clarify under which conditions migration can have developmental effects and under which it will be contrary to the advancement of home communities and countries. Policy implications of this analysis, in particular the role of governments in sending and receiving nations, are examined.