Theoretical and practical aspects of the use of uniform (authorized) title for anonymous works and works by individual authors in the union catalogues of Croatia and Slovenia are examined. Libraries in the two countries use the same cataloguing code, Eva Verona's Pravilnik i priručnik za izradbu abecednih kataloga. Their union catalogues CROLIST (Croatia) and COBISS (Slovenia) are based on UNIMARC bibliographic and authority formats. The two documents offer possibilities of crossreferencing original titles and translations, entire works and their parts (e.g., parts of and the entire trilogy) whenever that would be convenient for the user. The empirical investigation of the two catalogues performed in 2010 shows that only 27,4 % in (CROLIST) and 13,6 % (COBISS) of works with a known individual author lack this reference. Anonymous works more frequently lack this information: 47,3 % (CROLIST) and 55% (COBISS). This is rather discouraging since the uniform (authorized) title is essential for bringing cataloguing records together to fulfil three cataloging functions: to show whether the library has a particular book, which editions of a work, and which works of an author there are in the collection. This information is also essential for frbrization of the library catalogue. Although there are some problems in UNIMARC formats in reporting the original title, the use of the field 500 and of the national cataloguing rules is extremely important.