Vulnerability in research is often understood as a diminished ability to protect one's own interests, manifested by a compromised capacity to give informed or voluntary consent. Certain groups of people are thought to be more vulnerable than others and therefore are at risk of being exploited or mistreated in research. Accordingly, the federal regulations call for additional safeguards to protect vulnerable groups.There remains some ambiguity and contradiction, however, regarding what groups are vulnerable in research and why,3 since the available codes (...) of research ethics and regulations describe many groups as vulnerable. When so many groups are considered vulnerable, but no specification is offered as to how they are vulnerable or what particular protections are appropriate, the possibility of meaningful safeguards is diminished. In addition, current concepts of vulnerability are usually applied to whole groups of people, without distinguishing between individuals in a group who might truly have a compromised capacity to protect their own interests from those who do not. (shrink)