Open Access Subset
The PMC Open Access Subset 
is a relatively small part of the total collection of articles in
PMC. Articles in the PMC Open Access Subset are still protected by copyright, but are made
available under a Creative Commons
or similar license that
generally allows more liberal redistribution and reuse than a traditional copyrighted work.
Please refer to the license statement in each article for specific terms of use. The license
terms are not identical for all articles in this subset. Note that:
- The majority of the articles in PMC are subject to traditional copyright restrictions and are not part of this subset. Read the PMC Copyright Notice for more information.
- The PMC OAI service and the PMC FTP service are the only services that may be used for automated downloading of articles from this open access subset.
- Systematic retrieval (bulk downloading) of articles through any other automated process is prohibited, even if you are only retrieving articles from this subset.
- Some journals use the label "open access" for an article that is available free at time of publication, but is still subject to traditional copyright restrictions. Such articles are not part of this subset.
The PMC Open Access Subset includes articles from a number of publishers' programs, each of which deposits selected articles from a range of journals. A complete list of the publisher programs, with links to the articles, can be found on the Special Collections tab of the PMC Journal List.
In addition to these selective deposit programs, a number of the journals that deposit their
complete contents in PMC include some or all their articles in the open access subset. These
journals are marked with the symbol in
PMC's Journal List.
To preview the articles or get a current count of articles in the OA subset, do a search for open access[filter] in PMC. Please note, however, that you may only use the two services mentioned below for automated (or bulk) retrieval of articles from the OA subset.
Use the OAI service to download XML for the full text of articles in this open access subset.
Use the FTP service to download a complete set of files — XML, images, PDF, and supplementary data files, if any — for articles in this subset. For users who are interested in just the XML, the FTP service also has a single zip file containing the XML files for all the articles in the open access subset.