Leading members of the gerontological community have recently launched a war on anti-aging medicine, seeking to discredit what they judge to be fraudulent and harmful products and therapies, and to distinguish their research from what they regard as the pseudoscience of the anti-aging movement. This article interprets the contemporary war on anti-aging medicine as largely an attempt by established gerontological researchers to preserve their hard-won scientific and political legitimacy, as well as to maintain and enhance funding for research on the basic biological mechanisms of aging. First, it recounts the difficult struggle of U.S. biogerontologists to join the scientific mainstream in terms of legitimization and public funding. Second, it examines how elements of a contemporary anti-aging movement seem to threaten the hard-won public legitimacy of established gerontological researchers and practitioners. Third, it looks at the "boundary work" responses of the gerontological community to the anti-aging movement. Finally, it assesses the consequences of the war on anti-aging medicine to date.