In 2004 we implemented an open access option whereby authors may pay a surcharge of $1,000 to make their article freely available online immediately upon publication. We believe that it is essential to involve institutions in open access for its long-term viability, so, beginning in 2005, each PNAS institutional site license (i.e., each institutional online subscription) will automatically include an institutional open access membership. Corresponding authors from such institutions may pay just $750 to make their papers immediately free online. We offer this plan without increasing our site license rates over 2004. We see a number of benefits to this new plan. First, a number of librarians have told us that they support a transition to open access. The purchase of a site license/open access membership provides a natural way for them to do so. Second, we hope that by adding value to the traditional site license we will encourage institutions to maintain their site licenses in these rapidly changing times for scientific publishing. Furthermore, we like the buffering aspect of the new plan. As the number of authors who choose open access increases, the value to the author's institution of a traditional site license decreases, but the value of the open access discount increases. For a typical mid-sized institution (see www.pnas.org/subscriptions for the 2005 PNAS site license rates), only nine authors need to choose open access for the institution's site license/open access membership to be free. Third, we hope that the 25% discount will encourage more authors to choose the open access option, which is off to an encouraging start. Please help us inform authors at your institution about the PNAS open access option, and urge your librarian to secure your site license/open access membership discount for 2005. Open access publishing is gaining momentum, but we believe that it cannot succeed solely on an author-pays basis; hybrid funding models are still needed. PNAS is a break-even, not-for-profit operation, and our funding sources include subscriptions to the print journal; author page, color, and reprint charges; and now the institutional site license/open access membership. One argument often used against adoption of open access is the difficulty of discerning a business path from the traditional subscription-based system to open access. The site license/open access membership provides a kinetically favorable pathway. We think other journals could do the same.