One of the major challenges in the post genomic era consists in exploiting the vast amounts of biological data stored in the numerous heterogeneous biological databases distributed worldwide. Most research projects in bioinformatics start with data retrieval from selected sources. However, identifying appropriate data sources is not trivial and requires the representation of the knowledge about data sources. We present here the BioRegistry project which aims at providing means to represent and exploit knowledge associated with biological databases. As a first step, a repository structure has been designed to organise metadata associated with databases consisting of five metadata categories: database identification, topics covered, quality information, access/availability, and tracking of the metadata. The BioRegistry model and its relationships with the DCMI (Dublin Core Metadata Initiative) are described. Prototypes with various functionalities to feed, maintain and exploit the repository are presented.