Medical Subject Headings
ASCII MeSH Documentation and Availability
1. ASCII MeSH
ASCII MeSH contains each of these three record types:
- Descriptor Data Elements
- Qualifier Data Elements
- Supplementary Concept Records (formerly Supplementary Chemical Records), Data Elements
2. Restrictions on use
There is no charge. Use of the ASCII MeSH file data is subject to conditions which are detailed in the Memorandum of Understanding.
The data for Descriptors and Qualifiers are updated annually and users of the data are encouraged to obtain the new year's data. Any changes made mid-year are included in the weekly update of ASCII MeSH files.
Supplementary Concept Records (formerly Supplementary Chemical Records) are updated at NLM Monday through Friday. Supplementary Concept Records (formerly Supplementary Chemical Records) are updated daily and released Monday through Friday. They are coordinated with MeSH descriptors so that the data elements that refer to specific descriptor, such as the <HeadingMappedTo> element, match the same release year. New records will be added to ASCII MeSH periodically.
4. File format
Each element or occurrence is contained on a single line. Each line contains an element name and value, for example,MH = Appendicitis
The same is true for longer, free-text fields such the Annotation and Scope Note.
For data elements that are multiply-occurring, each element occurs on a separate line, for example, the MeSH Tree Number:MN = E05.200.500.607.790
MN = E05.200.500.620.670.620
There are a few non-English entry terms having diacritic characters. For example, "Carbocaïne", a French trade name for the anesthetic Mepivacaine. Note the small "i" with dieresis, is known in French as the tréma. These characters are encoded in Unicode UTF-8 format and will be correctly displayed by UTF-8 applications. File extensions are .bin rather than .txt so that Web browsers will prompt to save rather than automatically trying to display the relatively large text files.