Although attention has been paid to the massive number of people incarcerated in the US, the health systems within this sprawling detention system have largely been obscured from public attention. In this issue of JAMA Internal Medicine, Lupez and colleagues¹ use data from the Bureau of Justice Statistics’ 2016 Survey of Prison Inmates and find that, compared to 2004, the prevalence of physical and mental health conditions increased, as had the number of people who reported a need for medical care but did not obtain services. Across health conditions, the percentage of people who reported not using needed health services while incarcerated ranged from 9% of pregnant people who had no obstetric examination to 43% of people with chronic mental health conditions.