Introduction: Clinical research is essential for the advancement of Medicine, especially regarding the development of new drugs. Understanding the reasons behind patients' decision of participating in these studies is critical for the recruitment and retention in the research.
Objectives: To examine the decision-making of participants in biomedical research, taking into account different settings and environments where clinical research is performed.
Methods: A critical review of the literature was performed through several databases using the keywords: "motivation", "decision", "reason", "biomedical research", "clinical research", "recruitment", "enrollment", "participation", "benefits", "altruism", "decline", "vulnerability" and "ethics", between August and November 2013, in English and in Portuguese.
Results: The review pointed out that the reasons can be different according to some characteristics such as the disease being treated, study phase, prognoses and socioeconomic and cultural environment. Access to better health care, personal benefits, financial rewards and altruism are mentioned depending on the circumstances.
Conclusion: Finding out more about individuals' reasons for taking part in the research will allow clinical investigators to design studies of greater benefit for the community and will probably help to remove undesirable barriers imposed to participation. Improving the information to health care professionals and patients on the benefits and risks of clinical trials is certainly a good start.