Using medical advances to enhance human athletic, aesthetic, and cognitive performance, rather than to treat disease, has been controversial. Little is known about physicians? experiences, views, and attitudes in this regard. We surveyed a national sample of physicians to determine how often they prescribe enhancements, their views on using medicine for enhancement, and whether they would be willing to prescribe a series of potential interventions that might be considered enhancements. We find that many physicians occasionally prescribe enhancements, but doctors hold (...) nuanced and ambiguous views of these issues. Most express concerns about the potential effects of enhancements on social equity, yet many also believe specific enhancements that are safe and effective should be available but not covered by insurance. These apparently contradictory views might reflect inherent tensions between the values of equity and liberty, which could make crafting coherent social policies on medical enhancements challenging. [Supplementary materials are available for this article. Go to the publisher's online edition of American Journal of Bioethics for the following free supplemental resource(s): An additional table (Table 5) referred to on p. 5]. (shrink)