Participants in research generally are reimbursed for expenses related to their participation, e.g. travel, meals and child or elder care. They also may be compensated for time, inconvenience and for risks they accept as part of the research. Determining a just level of compensation, and particularly one that is not an undue inducement or coercive for poor and/or disadvantaged research subjects, is another issue. When conducting research with children, with decisionally impaired adults, or with a community, who should be compensated?