Résumé : Background: The goal of this health-psychology study was to investigate the range of motives that make someone consent or refuse participation in a clinical transplant trial. Methods: The study involved (i) preparatory interviews with five transplant patients who took part in clinical trials and five persons from the general public; (ii) we created a questionnaire with scaled responses; (iii) we selected 468 patients, divided into two groups: patients waiting for a transplant and patients who already had a transplant; (iv) we obtained patient consents, sent out the questionnaire, and recorded responses; (v) data were analysed using descriptive statistics, exploratory factorial analyses, correlations and regressions. Results: Two hundred and ten patients answered the questionnaire. Motives were classified into the following: (i) Motives to consent participating in a clinical trial (pride in participating, hope for better quality of life, sufficient and clear information, discussion with others participating in a trial, altruism); or (ii) Motives to refuse participating (no information on medical teams, lack of explanation, fear of additional expenses, being considered a "guinea pig"). Conclusions: This study contributes to our understanding of the motivations of patients who accepted or refused participation in a clinical transplantation trial. © 2013 John Wiley & Sons A/S.