Prisons have become the primary health care provider for some of the poorest and sickest women in the United States. By virtue of both biological sex and gender, incarcerated women have health needs different from those of their male counterparts. The purpose of this qualitative investigation was to understand better women's perceptions of how prison has affected their physical health. We conducted this investigation in a maximum-security women's prison in the United States using focus group methodology (12 focus groups, made up of 65 women). Women described several specific prison-based factors that affected their physical health: limited and complicated access to care; nutritional concerns; limited physical activity; and smoking in prison. We discuss these findings in relation to the gender-based health issues facing incarcerated women.