Nanomedicine shows tremendous promise for improving medical diagnosis, treatment, and prevention, but it also raises a variety of ethical concerns. Because of the paucity of data on the physicochemical properties of nanoscale materials in biological systems, clinical trials of nanomedicine products present some unique challenges related to risk minimization, management and communication involving human subjects. Although these clinical trials do not raise any truly novel ethical issues, the rapid development of nanotechnology and its potentially profound social and environmental impacts, add a sense of urgency to the problems that arise.