[Law and the Future of War Research Paper No 1] Technologically advanced armed forces have begun exploring ways to improve the warfighter as a living organism. The relevant practices could be called “biomedical human performance enhancement,” which sets them apart from more conventional ways of improving performance, such as training and equipment. Human enhancement raises a range of ethical, legal and social issues – both in the military context and in society more broadly. In the military context, issues arise under the law of armed conflict (LOAC). After providing a brief conceptual and technical background to human enhancement, this paper considers a set of LOAC issues relating to human enhancement by asking two broad questions: First, does LOAC prohibit or restrict the enhancement of warfighters? Second, if warfighters are enhanced in some way, what consequences does that have under LOAC?