Many immigrants in the United States are working-age taxpayers; few are elderly beneficiaries of Medicare. This demographic profile suggests that immigrants may be disproportionately subsidizing the Medicare Trust Fund, which supports payments to hospitals and institutions under Medicare Part A. For immigrants and others, we tabulated Trust Fund contributions and withdrawals (that is, Trust Fund expenditures on their behalf) using multiple years of data from the Current Population Survey and the Medical Expenditure Panel Survey. In 2009 immigrants made 14.7 percent of Trust Fund contributions but accounted for only 7.9 percent of its expenditures—a net surplus of $13.8 billion. In contrast, US-born people generated a $30.9 billion deficit. Immigrants generated surpluses of $11.1–$17.2 billion per year between 2002 and 2009, resulting in a cumulative surplus of $115.2 billion. Most of the surplus from immigrants was contributed by noncitizens and was a result of the high proportion of working-age taxpayers in this group. Policies that restrict immigration may deplete Medicare’s financial resources.