Perhaps the greatest power of folksonomies, especially when set against controlled vocabularies like the Library of Congress Subject Headings, lies in their capacity to empower user communities to name their own resources in their own terms. This article analyzes the potential and limitations of both folksonomies and controlled vocabularies for transgender materials by analyzing the subject headings in WorldCat records and the user-generated tags in LibraryThing for books with transgender themes. A close examination of the subject headings and tags for twenty books on transgender topics reveals a disconnect between the language used by people who own these books and the terms authorized by the Library of Congress and assigned by catalogers to describe and organize transgender-themed books. The terms most commonly assigned by users are far less common or non-existent in WorldCat. The folksonomies also provide spaces for a multiplicity of representations, including a range of gender expressions, whereas these entities are often absent from Library of Congress Subject Headings and WorldCat. While folksonomies are democratic and respond quickly to shifts and expansions of categories, they lack control and may inhibit findability of resources. Neither tags nor subject headings are perfect systems by themselves, but they may complement each other well in library catalogs. Bringing users' voices into catalogs through the addition of tags might greatly enhance organization, representation, and retrieval of transgender-themed materials. (Contains 1 figure and 2 tables.)