This paper describes the role of the Dublin Core Terms application profile in the management of crosswalks involving MARC in OCLC’s Crosswalk Web Service. This service, described in Godby, Smith and Childress (2008), formalizes the notion of crosswalk (Getty, n.d.) by hiding technical details and permitting the semantic equivalences to emerge as the centerpiece. As a result, metadata experts, who are typically not programmers, can enter the translation logic into a spreadsheet that can be automatically converted into executable code. The Crosswalk Web Service supports many mappings involving standards for describing bibliographic metadata, but the complex relationships among MARC and Dublin Core are especially compelling because they would be far less elegantly managed without the conceptual model of the application profile and the computational model of the crosswalk. With its focus on elements that can be mixed, matched, added, and redefined, the application profile (Heery and Patel, 2000) is a natural fit with the translation model of the Crosswalk Web Service, which attempts to achieve interoperability by mapping one pair of elements at a time. Users can test the service with their own records by accessing the public demo on the OCLC ResearchWorks page, or by invoking the Dublin Core export functions in OCLC’s Connexion® Client.