The ZBW German National Library of Economics—Leibniz Information Centre for Economics is the world’s largest economics library. It holds more than four million media items such as books, articles, journals, grey literature and databases. ZBW supports its users with fine-grained thematic access to these information resources. For this purpose the STW Thesaurus for Economics has been developed and applied since the 1990s. It provides a high-level taxonomy of subject categories, thousands of keywords (“descriptors”) and tens of thousands of both synonyms and links between the thesaurus concepts. The media items are indexed with descriptors from this thesaurus. They can be retrieved by these descriptors through the library catalog ECONIS.