The Open Terminology Services (OTS) project provides a common, well-specified mechanism to access terminological content in a vendor and platform neutral fashion. The project includes a freely available API specification and an open source reference implementation. The API specification derives from the OMG Lexicon Query Services interface specification as a foundation and defines mechanisms for browsing, querying and import terminological content. The Java-based reference implementation uses the Lightweight Directory Access Protocol (LDAP) for a back end, and provides a mechanism to query and distribute heterogeneous terminological content using a common format. The project includes the CTS (Central Terminology Services) subset under HL7.