Dear Colleague,

I am writing to you and to the other signers of the Public Library of Science's "open letter" to provide a brief update on progress at PLoS and to tell you about an unusual opportunity to offer further help to PLoS.

Since you pledged your support for enhanced access to the scientific literature, PLoS has been transformed. We began in 2000 as an organization advocating changes in publishing practices, but since 2003 we have been demonstrating the importance of such changes by becoming the world's most prominent publisher of open access journals in biology and medicine.

Today, PLoS publishes 6 peer-reviewed freely accessible online journals, all readily viewed, searched, downloaded, and used without restriction online. Articles in PLoS journals are highly regarded by the scientific community, commonly cited in other research reports, and frequently covered in international media. Our next launch will be PLoS ONE —an innovative interactive publishing forum that will exploit the full potential of the web to make the most of all rigorously— performed science.

As PLoS continues to grow and innovate, we will continue to require outside financial support to hire outstanding staff, develop new software, provide the infrastructure for new journals, and continue our work as advocates for open access publishing. Our revenue from authors' fees is increasing, and we are developing revenue streams from other sources, such as online advertising; but in the first several years of our development as a nonprofit publisher, we expect to depend on additional outside funding as an essential component of our sustainability.

Our major funders —Herb and Marion Sandler and the Gordon and Betty Moore Foundation— remain committed to PLoS; they have invested heavily in the organization because they strongly support our mission to make the world's scientific and medical literature a public resource.

To encourage us to involve a greater number of our supporters in the philanthropic effort, the Sandlers and the Moore Foundation have created a challenge grant to benefit the ongoing work at PLoS. They will match every dollar donated to us this year, if we can raise US$1 million by the end of this year.

Through the generosity of other donors, we are already more than half-way to the goal. I am writing to encourage you to make a contribution to PLoS today, small or large. Each donation will be doubled by our major funders and each donation, whatever its size, represents an important endorsement of the open access movement. With the click of your computer mouse, you can help the open access movement bring new discoveries directly to the people that will benefit from them.

You can make your donation online now through our secure website at http://www.plos.org/support/challenge.php

With thanks for your continued support,

Harold Varmus
Chairman, Public Library of Science