UNLABELLED: OBJECTIVE - METHOD: The purpose of this review is to explore the expectations of patients and physicians prior to participate to a clinical trial and their positive or negative experiences after participating. A systematic review of Medline database from 1966 to 2005 identified 79 papers reported patients and physicians perceptions of clinical trials (only 3 in French), whom 27 English surveys conducted on patients and physicians. RESULTS: If primary patients' motivation for enrolment was altruistic, physicians wish to help their patient. After enrolment, the most perceived positive benefit for patients and physicians are, respectively, the emotional improvement and the greater opportunity for personal benefit offered to enrolled patients. Most physicians' negative experience included logistical difficulties while patients are unease with randomisation and often uncomfortable with medical procedures. Unlike patients, all physicians' expectations seem to be fulfilled. CONCLUSION: The knowledge of patients' and physicians' perception of participation may improve recruitment in clinical trials.