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Unified Medical Language System® (UMLS®)


MetaMap is a highly configurable application developed by the Lister Hill National Center for Biomedical Communications at the National Library of Medicine (NLM) to map biomedical text to the UMLS Metathesaurus or, equivalently, to identify Metathesaurus concepts referred to in English text. MetaMap employs a knowledge-intensive approach, natural-language processing (NLP), and computational-linguistic techniques, and is used worldwide in industry and academia. At NLM, MetaMap is one of the foundations of NLM's Medical Text Indexer (MTI), which is applied to both semiautomatic and fully automatic indexing of biomedical literature. For more information on MetaMap and related research, see MetaMap Portal and Indexing Initiative (II).

Common uses of MetaMap include:

  • Information extraction
  • Classification/categorization
  • Text summarization
  • Question answering
  • Data-mining
  • Literature-based discovery
  • Text understanding
  • UMLS concept-based indexing and retrieval
  • Natural-language analysis of biomedical literature and clinical text


  • Downloadable binary and full sources available
  • Downloadable UMLS-based datasets for various UMLS releases
  • DataFileBuilder suite, which allows users to create their own data sets
  • MetaMap Java API to a local MetaMap installation
  • Web API to our Batch and Interactive scheduling facility (currently 120 ~3GHz processors)
  • MetaMap UIMA Annotator, which encodes MetaMap named entities in a format utilizable by UIMA components
  • MedPost/SKR part-of-speech tagger server and Word Sense Disambiguation (WSD) server

Minimum requirements (Full List of Prerequisites):

  • Current UTS account
  • 7 GB disk space for software
  • 1 GB minimum memory, with 2 GB or more recommended

MetaMap is intended to be easy to download, install, and run out of the box. Site-specific customization of MetaMap is expected; however, users desiring to create their own data files will need a moderate amount of programming knowledge to use our DataFileBuilder suite; users wishing to modify the MetaMap source code will need programming expertise in Prolog and a SICStus Prolog license, available from the Swedish Institute of Computer Science.

We Welcome Your Comments
If you have questions or comments regarding any aspect of MetaMap, please contact us at

Last Reviewed: July 29, 2016