Xu T - Patients may receive surprise medical bills from hospitals, often unknowingly, in context to receiving care from an out-of-network physician; these bills are typically several times the cost of care from an in-network physician and can be financially disastrous. In this cross-sectional study, markups are characterized from 2012 through 2016 and associations of markup with hospital characteristics are examined by focusing on charges in 2 specialties common in surprise medical billing, emergency medicine, and anesthesiology, using internal medicine as a reference. As per prior research, hospitals and departments within hospitals differ widely in hospital charge master prices, especially the “markups” greater than Medicare reimbursement rates in medical bills for out-of-network care. As of September 2019, several approaches are being considered by the US Congress to protect patients from surprise billing, including restricting the degree of markup.