hide You are viewing an archived web page, collected at the request of using Archive-It. This page was captured on 14:16:13 Mar 12, 2018, and is part of the National Library of Medicine collection. The information on this web page may be out of date. See All versions of this archived page. Loading media information
Skip Navigation Bar

Fact Sheet
NLM Classification

The NLM Classification Online

The National Library of Medicine Classification is published annually online (//www.nlm.nih.gov/class/). The print publication ceased with the 5th revised edition in 1999.

The online environment offers many advantages to users including hyperlinks between class numbers in the index and the schedules, and between terms within the index and direct links from these to the MeSH record itself under the MeSH Browser. It gives NLM the ability to keep the NLM Classification current with changes in MeSH.

Scope and Arrangement

The NLM Classification covers the field of medicine and related sciences. The scheme is a system of classification intended to be used for the shelf arrangement of all library materials, regardless of format. Designed as a broad classification, it is suitable for both large and small library collections and may be adapted to handle specialized collections of any size.

The NLM Classification is a system of mixed notation patterned after the Library of Congress (LC) Classification where alphabetical letters which denote broad subject categories are further subdivided by numbers. The NLM Classification utilizes schedules QS-QZ and W-WZ, permanently excluded from the LC Classification Schedules and is intended to be used with the LC schedules which supplement the NLM Classification for subjects bordering on medicine and for general reference materials. The LC schedules for Human Anatomy (QM), Microbiology (QR), and Medicine (R) are not used at all by the National Library of Medicine since they overlap the NLM Classification.

The headings for the individual schedules are given in brief form (e.g., WE - Musculoskeletal System; WG - Cardiovascular System) and together they provide an outline of the subjects that constitute the NLM Classification. These headings are interpreted broadly and include the physiological system, the specialty or specialties connected with them, the regions of the body chiefly concerned and subordinate related fields. The Classification is hierarchical, and within each schedule, division by organ usually has priority. Each main schedule, as well as some sections within a schedule, begins with a group of form numbers ranging generally from 1-49 which are used to classify materials by publication type, e.g., dictionaries, atlases, laboratory manuals, etc.

The main schedules QS-QZ, W-WY, and WZ (excluding WZ 220-270) are used to classify works published after 1913; the 19th century schedule is used for works published 1801-1913; and WZ 220-270 is used to provide century groupings for works published before 1801 and Americana. Geographic subdivision is provided for certain subjects in the NLM schedules by the application of Table G notations.



Preclinical Sciences:

  • QS Human Anatomy
  • QT Physiology
  • QU Biochemistry. Cell Biology and Genetics
  • QV Pharmacology
  • QW Microbiology and Immunology
  • QX Parasitology
  • QY Clinical Pathology
  • QZ Pathology

Medicine and Related Subjects:

  • W General Medicine. Health Professions
  • WA Public Health
  • WB Practice of Medicine
  • WC Communicable Diseases
  • WD Disorders of Systemic, Metabolic, or Environmental Origin, etc.
  • WE Musculoskeletal System
  • WF Respiratory System
  • WG Cardiovascular System
  • WH Hemic and Lymphatic Systems
  • WI Digestive System
  • WJ Urogenital System
  • WK Endocrine System
  • WL Nervous System
  • WM Psychiatry
  • WN Radiology. Diagnostic Imaging
  • WO Surgery
  • WP Gynecology
  • WQ Obstetrics
  • WR Dermatology
  • WS Pediatrics
  • WT Geriatrics. Chronic Disease
  • WU Dentistry. Oral Surgery
  • WV Otolaryngology
  • WW Ophthalmology
  • WX Hospitals and Other Health Facilities
  • WY Nursing
  • WZ History of Medicine. Medical Miscellany
  • 19th Century Schedule

The Index to the NLM Classification consists primarily of Medical Subject Heading (MeSH) concepts used in cataloging. It includes concepts first appearing in the latest edition of MeSH and other older concepts as warranted by the literature cataloged. It also provides access to classification numbers through these MeSH concepts. Index entries are updated annually to reflect additions and changes of the latest edition of MeSH.

Downloading the NLM Classification in HTML or PDF format.

Obtaining the NLM Classification Poster.

For further information on the NLM Classification, write:

Cataloging Section
National Library of Medicine
8600 Rockville Pike
Bethesda, MD 20894

Phone: 301-496-5497
Fax: 301-402-1211
Email: custserv@nlm.nih.gov
Cataloging Section home page on the Web: //www.nlm.nih.gov/tsd/cataloging/mainpge.html

A complete list of NLM Fact Sheets is available at:
(alphabetical list):
(subject list):

Or write to:

Office of Communications and Public Liaison
National Library of Medicine
8600 Rockville Pike
Bethesda, Maryland 20894

Phone: (301) 496-6308
Fax: (301) 496-4450
email: publicinfo@nlm.nih.gov