Health terminologies have become more complex, more massive, and more ubiquitous in the modern healthcare enterprise. Present technology makes the use of these terminologies by humans, unaided by machines, virtually impossible. However, system and message interoperability can be severely compromised if the software services deploying terminology content and interfaces are themselves non-standard. We review some characteristics for good terminology services and introduce an open-source, robust, widely deployed and widely available software resource to underpin terminology service implementations. The Lightweight Directory Access Protocol, or LDAP, is compared with alternative technologies. We describe a reference implementation of terminology services built around the HL7 Common Terminology Services using LDAP methods. We propose that LDAP is well suited as a common platform for federated, synchronized, and algorithmically distributed terminology content from multiple sources.