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Unified Medical Language System® (UMLS®)

UMLS Knowledge Sources: File Downloads

Release Information
MetamorphoSys Installation Help

2018AB UMLS Release Files

Release Description Date
Full Release ( The full release includes every vocabulary in the Metathesaurus, including those that are not actively updated. November 5, 2018

For users who wish to automate the download of the UMLS releases, we created scripts for Windows and Mac/Linux/Solaris computers. Combine the scripts with a scheduling tool to automate your downloads. You can download the scripts, along with a README file with instructions.

Download Notes:

  • Download the UMLS zip file and extract the contents to a single directory.
  • Read the README file after downloading, which includes information on installing the UMLS Knowledge Sources and highlights changes for this release.
  • Additional documentation is available at
  • At 1M bits/second, it will take approximately 4 hours to download the complete UMLS release. Use a high-speed internet connection to download the files.
  • Each UMLS release includes MetamorphoSys, required to install Knowledge Sources files, and to create, search and browse customized Metathesaurus subsets. MetamorphoSys requires a minimum of 30 GB of free hard disk and takes 2-10 hours to run on a range of platforms tested. The actual time will depend on your configuration, hardware and operating system platforms.

Active Release Change
NLM ceased production of the separate Active Release download for each UMLS Release. This change is effective with the 2017AB Release. The Full Release includes the option to select the Active Subset during installation (see picture below this paragraph). It is one of the options in the Default Subset Configuration window. The Active Subset is equivalent to the Active Release.

Metamorphosys - Select Default Subset Configuration window

UMLS Release Archives 2004-2018AA
UMLS Release Archives 2002-2003