Objective—To explore the opinions of unpaid healthy volunteers on the payment of research subjects.Design—Prospective cohort.Setting—Southern Alberta, Canada.Participants—Medically eligible persons responding to recruiting advertisements for a randomised vaccine trial were invited to take part in a study of informed consent at the point at which they formally consented or refused trial participation. Of 72 invited, 67 returned questionnaires at baseline and 54 at follow-up.Outcome measures—Proportions of persons who agreed or disagreed with three close-ended statements on the payment of research subjects; themes (...) and categories identified by content analysis of responses to an open-ended question.Results—A minority agreed with paying either patient or healthy volunteer participants. Opinions did not change over time. Participants' comments addressed: benefits and drawbacks to research participation; benefits and drawbacks to paying research participants; conditions under which payment of research subjects would be acceptable, and the nature of acceptable recognition. Acceptable conditions were to improve problematic recruitment, to reimburse costs, and to recognise participants, particularly for their time investment. Both non-monetary and monetary recognition of volunteers were thought to be appropriate.Conclusions—Most unpaid volunteers disagreed with paying research participants. The themes arising from their comments are similar to those that have been raised by ethicists and suggest that recognising the time and effort of participants should receive greater emphasis than presently occurs. (shrink)