There exist two assumptions that may well be connected. The first is that in an increasingly global and technological world, language barriers have fallen. Online machine translation services are monetarily free for everyone to use. So why is working with multilingual material so difficult in the library context? The second assumption is that the library catalogue is a technical fossil that has long been surpassed by the search and retrieval performance of the World Wide Web. Isn't the library catalogue simply a technical necessity of little interest? This study addresses the challenges and opportunities of the multilingual Online Public Access Catalogue (OPAC) as a key interface between librarians and end-users. The multilingual OPAC as interface definesaccess (for whom, to what, where). The competences, technology, and standards that come into play in an OPAC to access library references irrespective of the query language are investigated. The study combines a case study looking at the Swedish library context, its multilingual acquisition, and cataloguing workflows, with an evaluation of three selected OPACs to assess if and to which extent an OPAC can perform across languages.