Abstract. This paper describes an approach to SKOS vocabulary mapping that takes into account the context in which vocabulary terms are used in annotations. The standard vocabulary mapping properties in SKOS only allow for binary mappings between concepts. In the BestMap ontology, annotated resources are the contexts in which annotations coincide and allow for a more fine grained control over when mappings hold. A mapping between two vocabularies is defined as a class that groups descriptions of a resource. We use the OWL 2 features for property chains, disjoint properties, union, intersection and negation together with careful use of equivalence and subsumption to specify these mappings.