Current analyses of Mexico–U.S. migration theory generally are based on socioeconomic contexts and decision-making processes of male respondents. Further, limited data available on undocumented Mexican immigrant women mainly address the Mexico–U.S. border area, and adjacent U.S. urban centers. Our qualitative study focuses on undocumented Mexican immigrant women residing in central Washington State, where the regional economy is dominated by agribusiness development and dependent on immigrant and migrant farm labor. This paper assesses propositions of neoclassical economic and social capital theories of international migration in explaining the women’s migration decision-making processes. Project data indicate that while the Pacific Northwest has been a primary migration destination for sometime, it now may be increasingly a second-stage U.S. migration site, following initial migration to more traditional destinations such as California. In the Pacific Northwest, as well as nationally, Mexican immigrants—including those without documentation—have long provided a crucial labor force supporting, and at times rescuing, U.S. agribusiness enterprises. Particularly, in regions of the American West, where labor intensive, hand-harvested fruits and vegetables are the predominant farm crops, agribusiness development has encouraged a mobile, transient labor force (Martin, 1999; Taylor & Martin, 1997). This has contributed to a migrant flow from Mexico that is deeply rooted temporally, and broadly enmeshed socially, with communities in the United States (Thomas, 1985; Martin & Midgley, 1999). U.S. immigration policies aimed at curtailing undocumented immigration appear, at best, to be generally ineffective. At worst, they may prove counterproductive, creating “… an undocumented population that is markedly poor, less healthy, less educated, and more tenuously connected to the rest of society” (Massey & Espinosa, 1997, p. 991). Neither the U.S. political economy nor its immigration policies provide reason to anticipate much, if any, reduction in the undocumented immigrant Mexican population. Despite significant associated human costs, including both traumas of the border crossing experience and the difficult “lived experience” that follows for most in the United States, the steady flow of undocumented immigrants continues. And now, demographic estimates indicate that undocumented Mexican women, and particularly those accompanied by children, are migrating to the United States in increasing numbers. Theoretical frameworks for explaining international migration have focused on men. Where mentioned, women are incorporated as a component of the male study respondents’ “social capital,” or network of social ties that influence potential costs, risks and benefits associated with the men’s migration (cf. Massey & Espinosa, 1997, p. 953, 970). Immigration demographics highlight the need to begin assessing the applicability of extant theoretical models for understanding women’s migration decisions and circumstances, particularly as they intersect with fate of minor children. A growing selection of explicitly gendered field studies have begun to reveal even greater complexity in Mexican immigration history (cf. Del Castillo, 1990; Donato, 1993 and Hondagneu-Sotelo, 1994), but much more information is required to adequately evaluate whether women’s migration is governed by unique decision making processes. Further, the limited data available on undocumented Mexican immigrant women follows the bulk of migration studies in focusing on the U.S.–Mexico borderlands (Southwest, California) and adjacent U.S. “gateway” urban centers (cf. Chavez, 1990 and Chavez, 1998; Chavez, Hubbell, Mishra, & Valdez, 1997). Broadening the scope of inquiry beyond the borderlands poses significant questions about extrapolating from extant data, and may identify emerging second-stage migration patterns that should be incorporated into immigration analyses. Our interdisciplinary, qualitative study focused on undocumented Mexican women immigrating to, and residing in, the Pacific Northwest. Little is known about this population although Yakima County, located in central Washington, appears to include the state’s largest single group of undocumented women. In this region, the Yakima Valley Farm Workers Clinic (YVFWC) has addressed the health care and social service needs of migrant and seasonal farm workers, immigrants, and those without financial resources, for over 20 years (YVFWC, 1998).1 Undocumented immigrants are an important segment of YVFWC’s target population, and those served by the Farm Workers clinics were the source of our study sample. We sought to understand what factors compelled them—and particularly women with children—to risk crossing the Mexican-U.S. border, how they came to live in Yakima County, and to assess several factors related to their health status. In this paper, we examine the women’s crossing and settlement histories, including critical features of the social context, and costs, of their migration. More specifically, elements of neoclassical economic and social capital theories of international migration, developed from studies on men’s patterns, are evaluated qualitatively for their contribution to explaining our study participants’ migration decision-making processes.