Every year, millions of people sign up to participate in human clinical trials designed to test whether new drugs and other treatments in the development pipeline are effective. For the big pharmaceutical companies and major university labs running these studies, the results are the difference between the next billion dollar blockbuster (or endowment) and going back to the chalkboard. But for the participants, the trials are often a last-ditch effort to get better, or a personal sacrifice to help others like them survive.

And for years, the results of many of these trials remained buried in the private files of the companies that funded them, out of reach of the human volunteers—and other researchers working on similar scientific endeavors.

A new rule (PDF) issued Friday (Sept. 16) by the US Department of Health is designed to increase transparency around the methods and results of these trials, in an effort to “honor our commitments to trial participants, who do so much to help society advance knowledge and improve health,” said National Institutes of Health director Francis Collins in a press statement.

The rule covers a lot of ground, but first and foremost it addresses what has become an ongoing problem in the world of clinical trials: the partial or complete lack of reporting of some studies. In particular, the new rules force pharma companies to publish the results of all the drugs they test—even those that do not make it to market. And if side effects of a treatment occur more than 5% of the time in the trial, researchers will have have to make that public, too.

“This has been a very opaque world up until to now,” US Food and Drug Administration commissioner Robert Califf said on a press call Thursday. ”These are tremendous changes.”

Not reporting these failed trials creates major scientific inefficiencies, as researchers may end up repeating costly studies that they had no idea already floundered. Making the full range of clinical trial data available to the public could also, according to the Health Department, help patients and their health care providers make wiser decisions about their treatment options.

Additional changes under the new rules include expanding the range of studies that must be publicly registered to include behavioral interventions (like diet or meditation), and requiring that researchers make clear in advance what methods they plan to use to analyze their results. They will also have to submit additional details about trial participants, like race and ethnic background.

Any study receiving NIH funding must comply by the new rules, which go into effect January 2017.

This isn’t the first time that federal regulators have attempted to establish standards around clinical trial data transparency. Technically, scientists have had to publish results of these studies on ClinicalTrials.gov since 2000. But until now, the rules have lacked clarity and contained plenty of loopholes. A 2015 study in the New England Journal of Medicine found that overall compliance was “generally poor.”

According to the Wall Street Journal, the NIH has a stick prepared for future non-compliers: Ignoring the new rules “may jeopardize future grant funding,” said Francis Collins. If the regulator sticks to its guns, that could have immense impact: the NIH invests over $30 billion dollars every year in medical research.