This paper provides new insights into the process of undocumented border crossing by examining both men and women in the process. We investigate differences in the ways in which men and women make their way across the well-guarded Mexico-U.S. border, and the extent to which men and women by the end of the 1990s were similar to, or different from, their counterparts who crossed before 1986 and the implementation of immigration policy designed to reduce undocumented migration. We find substantial differences in how men and women crossed the border without legal documents and in their chances of being apprehended. Our analysis makes clear that shifts in U.S. immigration policy after 1986 have led to women's greater reliance on the assistance of paid smugglers to cross without documents but men were more likely to cross alone. Moreover, immediately after 1986, women on first U.S. trips faced higher risks of being apprehended compared to women who migrated in the early 1980s, but men faced lower risks. After accumulating some U.S. experience, however, both women and men faced lower risks of being detected after 1986 compared to earlier in that decade.