Y We are making PNAS free online to everyone around the world. By the end of this year, all content should be free from the first volume in 1915 to articles published just 6 months ago. The articles will be on our web site (www. pnas. org) and on the National Library of Medicine’s PubMed Central (www. pubmedcentral. nih. gov). Y We have made PNAS content free online immediately upon publication to 145 countries that are struggling to develop their scientific infrastructure. The list of countries is available at www. pnas. orgmiscfaq. shtml. Y We have changed our copyright and permissions policy to make it easier for authors and readers to freely use material published in PNAS for educational purposes. PNAS now allows authors to post the PDF of their article on their web site, to post and update preprints, and to post webcasts. Anyone may reuse original figures and tables published in PNAS for educational purposes without having to request permission.

In this Editorial, we announce an experimental open access option for PNAS authors, whereby authors may pay a surcharge of $1,000 to make their article freely available online immediately upon publication. We are pleased to note that the first open access article appears in this issue and is by Yang and Purves (1), first published online in PNAS Early Edition on May 19, 2004. The benefits to science of unfettered access to the literature are obvious and unassailable. The challenge of open access is how to pay for it. This challenge is particularly important for PNAS, which operates as a nonprofit, breakeven operation and does not maintain contingency funds or capital reserves. PNAS does not receive funds from the National Academy of Sciences or from the government, nor are Academy activities supported with journal revenue. Although I have no doubt that open