Body Integrity Identity Disorder (BIID) is a very rare condition describing those with an intense desire or need to move from a state of ability to relative impairment, typically through the amputation of one or more limbs. In this paper, I draw upon research in critical disability studies and philosophy of disability to critique arguments based upon the principle of nonmaleficence against such surgery. I demonstrate how the action-relative concept of harm in such arguments relies upon suspect notions of biological (...) and statistical normality, and I contend that each fail to provide normative guidance. I then propose a critical theory of harm, one marked by substantive engagement with both empirical and reflective inquiry across the sciences, social sciences, and humanities. I conclude by discussing the implications of this theory and how it might enrich ongoing debates in bioethics, philosophy of disability, and the health humanities. (shrink)