This paper uses high-quality and previously unused data from the Mexican Family Life Survey (MxFLS) to examine the selectivity by labor market skill of male migrants to the United States, and how the selectivity of migrants changes as costs and beneÖts of migration change. We conÖrm that Mexican migrants are selected from the middle of the education distribution, and present similar evidence of ìintermediateî selection on a broader index of labor market skill that combines education, age/experience, and cognitive ability. However, after adjusting for di§erences in the cost of migration, as measured by plausible proxy variables, we Önd substantially less evidence of intermediate selection on education and the broader index of skill. Finally, we show directly that the decision to migrate is highly correlated with di§erential returns to skill and the costs of migration