The term research subject has traditionally been the preferred term in professional guidelines and academic literature to describe a patient or an individual taking part in biomedical research. In recent years, however, there has been a steady shift away from the use of the term 'research subject' in favour of 'research participant' when referring to individuals who take part by providing data to various kinds of biomedical and epidemiological research. This article critically examines this shift, reflecting on the different meanings evoked by the terms 'subject' and 'participant', as well as examining recent examples of patient activism in research. It concludes by suggesting that the wholesale unreflective adoption of the term 'participant' is inappropriate and provides instead a guide on how to determine the circumstances in which the terms subject, participant and activist should legitimately be used.