Welcome to the NIH Public Access Policy Guide, where you'll find a variety of resources to assist you in navigating the mandatory policy for NIH-funded investigators.
Requirements for other US federal agencies can be found here.
Beginning in 2008, the National Institutes of Health (NIH) made it mandatory for funded investigators to submit final versions of their manuscripts to PubMed Central, the National Library of Medicine's digital archive. All NIH grantees must deposit their peer-reviewed articles upon acceptance for publication and make them available to the public within 12 months after publication. The legislation came after many years of lobbying by advocacy groups for such open access language and just as many years of opposition by publishers. See the news release from the Alliance for Taxpayer Access, Dec. 26, 2007 for more details.
What this means for NIH-funded researchers.