The first question I discuss in this paper is whether we have a duty of rescue to make our organs available for transplantation after our death, a duty we owe to patients suffering from organ failure. The second question is whether political obligations, in particular the obligation to obey the law, can be derived from natural duties, possibly duties of beneficence. Such duties are normally seen as merely imperfect duties, not owed to anyone. The duty of rescue, however, is a perfect one, mainly because it applies to us when we are in a unique position to provide urgent help to a person in need. The basic idea of a natural duty account of political obligation is that such unique positions can be artificially created by institutionalized coordination schemes. The remaining problem is how any particular coordination scheme could claim our allegiance rather than any other. This problem can be solved in different ways in the organ donation case, and in respect to a limited set of political obligations, mainly negative ones. A natural duty account is best seen as a constitutive part of a multiple principle theory of political obligation.