The aim of this paper is to examine the impact of South-North migration on the economic development of Subsaharan African countries by comparing the economic costs and gains of this phenomenon. International migrations has both positive and negative effects on the countries of origin of migrants. We attempt to evaluate the net effect on sub-Saharan African countries by using recent data of Docquier & Marfouk (2004) on the origin and the level of qualifications of migrants living in OECD countries.