There has been a huge growth in the size and number of Private Military and Security Companies (PMSCs) in the last decade or so. In this context, the question of when, if ever, states should hire PMSCs to carry out military operations has gained particular urgency. In this paper, I defend the answer that states should do so whenever PMSCs will be the most effective agents available against a number of recent objections. All of these objections claim that considerations aside (...) from the relative effectiveness of PMSCs should bear on the question. Some argue that there is something inherently morally problematic with hiring PMSCs, and thus infer that they should sometimes not be hired even when they are the most effective agents available. Others point to undesirable side-effects that hiring PMSCs is thought to cause, and claim that these should be taken into account when deciding whether to hire them. I argue, however, that all of these further considerations are either irrelevant to the decision or reducible to effectiveness. (shrink)