According to Jerome Wakefield’s harmful dysfunction analysis of medical disorder, the inability of some internal part or mechanism to perform its natural function is necessary, but not sufficient, for disorder. HDA also requires that the part dysfunction be harmful to the individual. I consider several problems for HDA’s harm criterion in this article. Other accounts on which harm is necessary for disorder will suffer from all or almost all of these problems. Comparative accounts of harm imply that one is harmed (...) when one is made worse off, that is, worse off than one otherwise would have been. Non-comparative accounts imply that one is harmed when one is put into some kind of condition or state that is, in some way, bad in itself. I argue that whether harm is construed comparatively or non-comparatively, HDA’s harm criterion is problematic. I tentatively conclude that an analysis of medical disorder should not make use of the concept of harm. (shrink)