Discussions of research involving vulnerable populations have left the homeless comparatively ignored. Participation by these subjects in drug studies has the potential to be upsetting, inconvenient, or unpleasant. Participation occasionally produces injury, health emergencies, and chronic health problems. Nonetheless, no ethical justification exists for the categorical exclusion of homeless persons from research. The appropriate framework for informed consent for these subjects of pharmaceutical research is not a single event of oral or written consent, but a multi-staged arrangement of disclosure, dialogue, (...) and permission-giving. Payments and other rewards in biomedical research raise issues of whether it is ethical to offer inducements to the homeless in exchange for participation in drug studies. Such inducements can influence desperate persons who are seriously lacking in resources. The key is to strike a balance between a rate of payment high enough that it does not exploit subjects by underpayment and low enough that it does not create an irresistible inducement. This proposal does not underestimate the risks of research, which are often overestimated and need to be appraised in light of the relevant empirical literature. (shrink)