We are often faced with dilemmatic situations in which we must choose between alternative courses of action, both of which will have a bad outcome. It is commonly held that in such cases it is both uncontroversial and unproblematic that we have to choose the lesser evil. However, despite its frequent application in ethical decision-making, lesser evil reasoning is not well understood by most of its advocates and it thus occasions much misunderstanding and it presents a number of pitfalls. In (...) this paper I shall thus, first, analyse the concept of a lesser evil; second, offer a critical assessment of lesser evil reasoning; third, discuss the most common pitfalls writers tend to fall into; and finally, explore the application of lesser evil reasoning to choices under uncertainty. (shrink)