Medicaid is an important source of health care coverage for prison-involved populations. From 2011 to 2012, we surveyed state prison system (SPS) policies affecting Medicaid enrollment during incarceration and upon release; 42 of 50 SPSs participated. Upon incarceration, Medicaid benefits were suspended in 9 (21.4%) SPSs and terminated in 28 (66.7%); 27 (64.3%) SPSs screened prisoners for potential Medicaid eligibility. Although many states supported Medicaid enrollment upon release, several did not. We have considered implications for Medicaid expansion.