Factors contributing to the underuse of mammography screening by female Hispanic farmworkers aged 50 years and older in the Lower Rio Grande Valley were determined through home-based, Spanish-language personal interviews (N = 200). Questions covered adherence to screening mammography guidelines (mammogram within 2 years), healthcare access, sociodemographic characteristics, and theoretical constructs related to breast cancer screening in the literature. Multivariate findings indicated that adherent women were 3.6 times more likely to have health insurance. Self-efficacy for obtaining a mammogram and decisional balance were also significantly related to adherence; age, income, and education variables were not associated, perhaps because of restricted variation. Results indicate continuing efforts are needed to ensure that medically underserved migrant farmworker women have access to health care services. In addition, efforts to increase their self-efficacy in obtaining a mammogram and to counter negative attitudes and opinions by stressing the positive prognosis associated with early detection are warranted.