It is often argued that clinical research should not violate the Kantian principle that people must not be used merely as a means for the purposes of others. At first sight, the practice of clinical research itself, however, seems to violate precisely this principle: clinical research is often beneficial to future people rather than to participants; even if participants benefit, all things considered, they are exposed to discomforts which are absent both in regular care for their diseases and in other areas of daily life. Therefore, in this paper we will consider whether people are used merely as a means by being enrolled in clinical research. On the basis of recent studies of Kantian scholars we will argue that clinical research is compatible with the Kantian principle if the conditions of possible consent and end-sharing have been met. Participants are not used merely as a means if they have sufficient reasons to consent to being enrolled in clinical research and can share the ends of the researchers who use them. Moreover, we will claim that even if people are used merely as a means by participating in clinical research, it may not always be morally wrong to use them in this way.