The PMID is a unique number used by PubMed that is automatically assigned to each article when entered into PubMed. PubMed is an index of abstracts that indexes the literature within MEDLINE.  PubMed only provides access to citations and abstracts – not full text articles.  Because a PMID number only links to the abstract – and not the full article – in PubMed, it does not meet citation requirements of the NIH Public Access Policy.  In contrast, the PMCID number is assigned by PubMed Central, the NIH-sponsored public-access database that contains the full text of peer-reviewed articles. Since its creation in 2000, PubMed Central has served as a free digital archive of full-text biomedical and life sciences journal literature at the NIH. Beginning in 2005, PubMed Central has also been the designated repository for papers submitted in accordance with the NIH Public Access Policy and for those that fall under similar policies from other funding agencies. The PMCID is a unique reference number that is assigned to every article that is accepted into PubMed Central. PMCIDs are listed below the abstract in a PubMed record. Click here to learn how an article appears in PubMed Central.