In connection with research on humans, the term "vulnerability" is only appropriate to identify the special need for protection of certain sections of the population and individuals, if this term refers to the additional risk of certain groups of subjects. Authors who focus on the additional risk suffering of a subject group when defining vulnerability succeed in considering the specific worthiness of protection in a context-sensitive way. The attempt to define the risk-benefit assessment for vulnerable subject groups on a binding basis faces considerable difficulties. This assessment depends both on the research situation and on the test subject. The normative aspect of this decision could be solved by referring to Rawl's decision model of an original position. In cases where there is no benefit for the subject, arguments in the discussion of the risks and benefits that are based on a "group or overall benefit" and an "objective interest," cannot be fully sustained.