This paper, guided by the UNESCO Universal Declaration on Bioethics and Human Rights, assumes that regulators should aim to support the development of nanomedicine while, at the same time, putting in place whatever limits or safeguards are indicated by ethical considerations. Relative to this regulatory objective, it is argued that, notwithstanding the importance of precaution (characteristically, concerning health, safety, and the environment), ethical reflection needs to go both broader and deeper. It is suggested that, by attending to the basic matrix (...) of ethical debate and the “bioethical triangle” through which the matrix is currently articulated, the breadth, depth, and conflictual plurality of ethical concerns about nanomedicine will be clarified. In this light, the conventional thinking about precaution is revisited and concerns about human dignity and informed consent (under conditions of extreme uncertainty) are analysed. The paper concludes that, once the range of ethical pluralism is grasped, the extent of the challenge facing regulators will be more clearly appreciated. (shrink)