There are instances when “tagging” your terms is appropriate. For example, earlier in this tutorial we used the MeSH field tag to search for records indexed with the MeSH vocabulary of interest, or to limit to MeSH Major Topic (Module 2). Tagging with MeSH restricts your search to MEDLINE-indexed records and should be used only with an understanding of what you may be missing and a plan for searching non-indexed records (Module 2), if appropriate.

There are other situations in which you may need to tag to specify a particular search of PubMed. They include:

1. To search within a specific field in PubMed records
2. To turn off Automatic Term Mapping (ATM)
3. To turn off automatic explosion

This section of the module will outline how to use tags in these special circumstances.