The selection of immigrants by skill and education is a central issue in the analysis of immigration. Since highly educated immigrants tend to be more successful in host country labour markets and less of a fiscal cost it is important to know what determines the skill-selectivity of immigration. In this paper the authors examine the proportions of highly educated among migrants from around 80 source countries who were observed as immigrants in each of 29 OECD countries in 2000/1. They develop a variant of the Roy model to estimate the determinants of educational selectivity by source and destination country. The authors also estimate the determinants of the share of migrants from different source countries in each destination country's immigrant stock.