This chapter describes the involvement of healthy volunteers in biomedical research. Healthy individuals are valuable to research because they can offer data about biological processes or investigational products that are not distorted by illness or disease. In addition, healthy individuals are generally much easier to recruit to research than are ill patients. Recruitment of healthy participants is aided by the offer of financial compensation in exchange for their participation. The involvement of healthy individuals in research is meant to resolve ethical problems associated with enrolling patients, such as exposing sick individuals to risk and creating misunderstandings for patients about the difference between research and clinical care. However, as this chapter details, using healthy individuals in biomedical research raises different concerns about risk exposure as well as ethical dilemmas associated with paid research participation, the exploitation of vulnerable groups, and the validity of the data produced.