Studies of the ethics of medical and nursing research have focused principally on the more practical issues to do with the research process, such as informed consent and protection of subjects from harm A more fundamental question, which is often overlooked, is whether individuals are under any sort of obligation to participate as subjects in nursing research in the first place The conclusions which nurses reach on this issue will help establish the overall moral climate in which nursing research is conducted In this paper, three models of such an obligation are explored, one based on a notion of payment, one centred in the social contract, and one which seeks to estabbsh an unconditional obligation Each of these is seen to be flawed in various respects The delicate and potentially conflicting relationship between obligation and consent is then briefly examined In conclusion, it is argued that the notion of a ‘moral claim’ on participation in research is an ethically more acceptable approach than any strict sense of obligation