HASSET - the Humanities and Social Sciences Electronic Thesaurus - has been developed by The Data Archive at the University of Essex over a period of 18 years. In use with the Archive's own retrieval system BIRON, the thesaurus allows subject access to the Archive's collection of over 5,000 social science datasets.

The paper will describe the thesaurus, its subject coverage and structure, its maintenance and patterns of use. In particular, the paper will describe how, driven by the current Thesaurus Project, HASSET has entered a period of dynamic growth. It is being expanded from the existing collection based thesaurus to become a broadly based subject thesaurus for the social sciences. Increasingly it will reflect the requirements and contributions of its external users as candidate terms are suggested by co-operating organisations via a new Web based entry form.

New ways of delivering the thesaurus will be explored including the provision to co-operating bodies of the complete thesaurus to integrate into their own software environment, and the possibility of allowing for remote access to the Archive's indexing and retrieval software.