The Resource Discovery Network (RDN) has taken a collaborative approach to the development of a network of subject gateways, each of which offers a variety of services to its subject-focused community. This paper considers the use of the Open Archives Initiative Protocol for Metadata Harvesting as a mechanism for sharing metadata records between those gateways in order to build cross-subject resource discovery services. Keywords Resource discovery, subject gateways, content sharing, metadata, Dublin Core, XML, Open Archives Initiative, RDN.