One of the ways in which transnational medical agencies (TMAs) such as Medicins Sans Frontieres aim to increase the access of the global poor to health services is by supplying medical aid to people who need it in developing countries. The moral imperative supporting such work is clear enough, but a variety of factors can make such work difficult. One of those factors is the wrongdoing of other agents and agencies. For as a result of such wrongdoing, the attempt to supply medical aid can sometimes lead to significant negative effects. What should TMAs do in such situations? On one view, TMAs should take account of any negative effects arising from the wrongdoing of others in just the same way in which they take account of negative effects arising more directly from their own actions, or from natural forces. To many people, this view seems wrong. In this paper, I articulate and discuss several different reasons why one might think this. In doing so, I hope to contribute to a debate about the more general question of how TMAs should respond to the wrongdoing of others.