Glasgow University Library has successfully converted to MARC21. Preparation for this project took place over several months in consultation with their system suppliers, Innovative Interfaces Inc (III). However, the actual process of exporting their existing UK MARC bibliographic and authority files (almost 1 million records in all), converting them to MARC 21 and reloading them back to their system took just over 2 weeks. System downtime was not required, although amendments to bibliographic and authority records were not allowed during this time.