SUNCAT will be the UK national union catalogue of journals and other serials. It will have two aims: to be a 'digital library' locate service for serials held in other than one's own library and to be a source of good catalogue records to enable contributing libraries to upgrade their OPACs. SUNCAT is also the name given to the project that is carrying out the pilot activity: investigating the issues, engaging with research libraries, and preparing to launch a pilot service, before extending the scope to include over 200 libraries. The first phase of that project started in February 2003, and has involved loading the ISSN and CONSER databases, together with records on the item holdings of twenty-two of the larger research libraries, and converting these into MARC21 format. This paper presents the perspective of the team responsible for the design and implementation of SUNCAT.