Subject repositories are under-studied and under-represented in library science literature and in the scholarly communication and digital library fields. A study of practical literature on subject repositories reveals a relatively small proportion of practical articles to total articles found that discuss subject repositories in some way — where practical refers to articles that would help inform decisions on repository development and management. In addition to the lack of practical literature on subject repositories, registries, software, publishers, and database thesauri do not define subject repositories consistently, do not recognize subject repositories as distinct from other types of repositories, or do not recognize subject repositories at all. At the same time, subject repositories are frequently cited as highly successful scholarly communication initiatives, especially in relation to institutional repositories. The lack of subject repository recognition within the literature and among commonly used repository tools may be attributed to the isolated development of the largest subject repositories and a general lack of awareness about small-scale subject repositories. The authors recommend an increase of literature and research on subject repositories, development of standard language, guidelines, and best practices, and the formation of a community of subject repository professionals.