Using recent data from southern California and Mexico we challenge the notion that the demographic profile of post-1970 Mexican migrants to the United States has remained constant. We find that more recent cohorts of migrants: (1) are more likely to settle permanently in the United States, (2) have higher proportions of females, (3) are younger, (4) have higher educational attainment, (5) are increasingly likely to originate in southern Mexico and the Mexico City Metropolitan area, and (6) are increasingly likely to depart from urban areas within Mexico. Although we find no direct evidence that the legalization programs mandated by the Immigration Reform and Control Act of 1986 led to a stronger propensity to settle permanently in the United States, logistic regression analyses demonstrate the importance of the other three principal explanatory factors suggested by Cornelius (1992), namely, economic crisis in Mexico, the changing character of U.S. demand for labor, and social networks.