The shortage of transplant kidneys has spurred debate about legalizing monetary payments to donors to increase the number of available kidneys. However, buying and selling organs faces widespread disapproval. We survey a representative sample of Americans to assess disapproval for several forms of kidney market, and to understand why individuals disapprove by identifying factors that predict disapproval, including disapproval of markets for other body parts, dislike of increased scope for markets and distrust of markets generally. Our results suggest that while the public is potentially receptive to compensating kidney donors, among those who oppose it, general disapproval toward certain kinds of transactions is at least as important as concern about specific policy details. Between 51% and 63% of respondents approve of the various potential kidney markets we investigate, and between 42% and 58% want such markets to be legal. A total of 38% of respondents disapprove of at least one market. Respondents who distrust markets generally are not more disapproving of kidney markets; however we find significant correlations between kidney market disapproval and attitudes reflecting disapproval toward certain transactions—including both other body markets and market encroachment into traditionally nonmarket exchanges, such as food preparation.