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NLM Classification Updated, September 23, 2019

September 23, 2019

The NLM Classification, available online at, is updated two times a year.

The 2019 winter version, published January 31, 2019, encompassed changes to the NLM Classification resulting from new and changed 2019 Medical Subject Headings (MeSH) terms as well as additional minor updates to the index and schedule.

The 2019 summer version, published September 23, 2019, encompasses the systematic review of the QW (Microbiology. Immunology) and QX (Parasitology) schedules and other miscellaneous updates.

For more information about the scope of the 2019 summer edition, see

Contact NLM for further information, questions, or comments.

Since its founding in 1836, the National Library of Medicine has played a pivotal role in translating biomedical research into practice and is a leader in information innovation. NLM is the world's largest medical library, and millions of scientists, health professionals and the public around the world use NLM services every day.


Last Reviewed: September 23, 2019