International migration is associated with increased HIV vulnerability, but little is known about the vulnerability of internal migrants. This qualitative study explored perceptions of HIV and condom use among Mexican migrant female factory workers. Migration and male sexual infidelity contributed to increased HIV vulnerability and unprotected sex was ubiquitous. The dominant cultural discourse that dichotomizes "good" (monogamous) and "bad" (sexually stigmatized) women, and male partner's resistance, were barriers to condom use. Women's positive attitudes toward the dual protection (pregnancy and sexually transmitted infections) offered by condoms and sexual agency expressed by refusing unwanted sexual contact are resources for HIV prevention.