This paper examines the extent to which Mexican emigrants to the United States are negatively selected. Previous studies have been limited by the lack of nationally representative longitudinal data. This one uses a newly available household survey, that identifies emigrants before they leave. On average, U.S.-bound Mexican emigrants from 2000 to 2004 earn lower wages and have less (more for females) schooling than nonmigrant Mexicans, evidence of negative selection. This argues against Chiquiar and Hanson's (2005) findings. The discrepancy is primarily due to an undercount of unskilled migrants in U.S. sources and secondarily to the omission of unobservables in their methodology.