The HL7 Vocabulary Technical Committee (TC) was organized to select and maintain the vocabulary used in HL7 messages. The goal is to make implementations of the Version 3 HL7 Standard more plug-and-play compatible. In order to make the vocabulary readily accessible to the public, HL7 is collaborating with the U.S. National Library of Medicine (NLM) to include HL7 vocabulary in the Unified Medical Language System (UMLS) Metathesaurus. This article describes a proposal for how HL7 data elements and coded values can be represented accurately in the relational tables of the UMLS Metathesaurus.