Medical testing assesses individual bodies, yet its effects reach beyond their boundaries. Building on insights from medical anthropology and STS regarding the co-construction of medical technologies and bodies, I investigate how heterosexual Mexican couples used men’s HPV testing to understand and assert membership in collective ‘couple’s biologies’. I analyze interviews undertaken during men’s participation in a longitudinal, observational HPV study. Men underwent annual DNA-based HPV testing, often receiving unexpected diagnoses that led couples to deal with the possibility of HPV transmission and its possible harms. I argue that these couples drew on context-specific ideologies of gender and race in their understandings of and responses to men’s test results. I show how they understood HPV positivity as a condition of the couple’s biology, mediated by what participants viewed as potentially racially innate if problematically backward gender attributes. Couples then used the experience of medical testing to live out self-consciously modern forms of gender, marriage, and self-care, which they hoped would counteract the harms of HPV. I conclude by discussing the importance of considering context-specific collective biologies, rather than just individual bodies, in the use and social scientific study of medical technology.