YOU'VE JUST BEEN diagnosed with a disease you can barely pronounce, let alone understand. All you know, based on what the doctor has told you, is that things could get very serious if you don't start treatment. But there are two possible treatments, each with upsides and downsides. It's up to you to decide which one you want to try. So where do you turn?

Like a lot of people, you go online. If you know how to get good, peer-reviewed medical information on the Web, you go to the National Library of Medicine's database of scientific articles called, not very glamorously, PubMed (www.ncbi.nlm.nih.gov/PubMed). It's a pretty nifty site: you can search specifically for the names of the treatments your doctor has recommended and several dozen articles pop up on your screen. When you want to read the articles, however, you are stymied. All you get is a short abstract of the article – not enough to tell you what you need to know – and you have to cough up to $40 or $50 for the full text. Why can't you get free access to information that was paid for using your tax dollars?

That's what the activists at the Public Library of Science in San Francisco want to know, too. Led in part by Nobel laureate Harold Varmus and charismatic gene-chip whiz kid Michael Eisen, PloS's mission is to make scientific knowledge a public good.

The group traces its immediate history to Varmus's project PubMed Central, a service associated with the aforementioned PubMed, which was supposed to make the full text of articles available to anyone who wanted them. Unfortunately, the scientific publishing business – exemplified by corporate giants like Elsevier, which puts out thousands of periodicals and books – didn't exactly embrace the idea of making its copyrighted materials available for free.

To highlight the growing antagonisms between scientists and many of the journals that publish them, a coalition of researchers circulated a petition among their colleagues in 2000 calling for journals to make their contents publicly accessible. More than 30,000 scientists from all over the world signed it.

And so PloS was born. If scientific publications weren't willing to open up their contents to the world, members of PloS reasoned, then the scientists would have to start publishing their work in a new way. With a five-year, $9 million grant from the Gordon and Betty Moore Foundation under its belt, PloS is getting ready to launch two online scientific journals, PloS Biology and PloS Medicine. Articles in both publications will be written by leaders in the field and subjected to a rigorous peer-review process. Then they will be released under a public access license developed by Creative Commons, a group at Stanford University that develops legal alternatives to the restrictive copyright system PloS aims to challenge.

Vivian Siegel left a high-profile job as editor of Cell – one of the triumvirate of top scientific journals, along with Science and Nature – to work as executive director of PloS. Why make the move from one of the most influential scientific journals in the world to an upstart whose future is uncertain? "I'm an idealist," she says simply. Plus, if it comes to a showdown between science and publishing, the biologist turned editor is firmly on the side of science. "All the editors at Cell wanted to make our articles open-access, but [parent company] Elsevier didn't want to do it. When I pointed out that our position made me feel like I wasn't working for the benefit of the scientific community, my boss said, 'What? You think you're a scientist?' I realized I couldn't act on my principles and continue at Cell."

Lawrence Berkeley National Laboratory researcher and PloS cofounder Eisen says his passion for the PloS projects grew out of a frustrating experience he had in his work on DNA microarrays, tools that help biologists analyze genomic activity. A recent breakthrough in the technology allowed Eisen and his colleagues to look at an entire genome, which meant they were inundated with information about thousands of genes. Eisen thought the best way to deal with the situation would be to link the output from the array to software that would search databases of scientific literature for information about the relevant genes. When a researcher wanted to study a section of the genome, he or she could get information from the array and from the literature at the same time. But, according to Eisen, "the publishers said, 'No, it's our information.' That's when I recognized that the publishing system doesn't serve the scientific community. We couldn't build on other people's knowledge. It's a perversion of the principles of science."

For a researcher like Eisen, PloS could become the ideal research tool. Data about genomics is scattered across hundreds of publications; with open-access publication, all of that data would be at his fingertips. "My research is dependent on [PloS] succeeding," he says, and he's not alone. Most microbiology these days involves data aggregation. Without it, treatment for cancers – diseases caused by mutations in the genome – could be much further away than most of us hope.

"Sharing information is a key founding component of science," Eisen argues. "Today technology has made it easy to imagine a world where the free full text of every scientific paper is available to everybody in the universe." Of course, technology alone isn't enough. It's only as good as the people using it. And that's why PloS is a hopeful sign of things to come.