PurposeThe purpose of this article it to investigate the design, and to implement the set‐up of the national union catalogue for those serials which can be accessed at the research libraries of the UK, the aim being to: enable researchers to locate serials held; to assist upgrade of library OPACs; and to provide a component within the UK digital library.Design/methodology/approachThis article builds upon the RSLP‐funded and JISC‐funded scoping and feasibility studies. It makes best use of extant data in OPACs on serials holdings information, by a mixture of collaborative action by contributing libraries, ISSN‐IC and CONSER; and makes best use of extant software (Aleph 500) and national data services (EDINA).FindingsToday, knowing who has which journals online has become as important as knowing who has which journals on‐shelf. Knowledge of both is critical for a researcher in her quest to discover, locate and access that key article. Knowledge of both is also critical for the library profession, as help staff and as curators of quality bibliographic records for serials in their OPACs. SUNCAT has over four million records, describing the “print and electronic holdings” of over 20 of the largest UK libraries – thought to cover 90 per cent or more of the journal titles held across the UK as a whole. The extension of coverage to up to a further 50 research libraries is in progress. So too is development activity to meet the challenge of the digital, investigating how SUNCAT can offer an important link in the access/supply chain, as the focus shifts from document supply to document access.Originality/valueThis article is of significance to researchers and librarians in the UK; there is wider significance for the international serials community.