This open letter, issued in 2001 and signed by more than 30,000 scientists, urges publishers to allow research appearing in their journals to be distributed freely by independent, online public libraries of science.

Signatories to the letter also pledge that they will subcribe to, publish in, edit or review for, only those journals that have agreed to grant unrestricted free distribution rights to all research reports that they publish.

The letter was the first initiative of the Public Library of Science, a nonprofit organisation committed to making the world's scientific and medical literature a public resource. The organisation has now shifted its efforts to publishing its own journals, but it still encourages individuals to show their support for PLoS by signing the letter.