This HCUP Statistical Brief describes 2012 hospital stays with a primary expected payer of Medicaid and stays that were uninsured. This information represents an update to 2008 data presented in HCUP Statistical Brief #104. Hospital stays with an expected primary payer of private insurance are used as a comparison point for Medicaid and uninsured stays. Hospital and patient characteristics for hospital inpatient stays in 2012 are presented by expected primary payer. The most common diagnoses and the most common operating room (OR) procedures by expected primary payer also are provided. All differences in mean estimates and proportions between expected payers noted in the text are statistically significant at the .0001 level or better.