A study published today in Science may shed new light on why African American scientists are so rare in biomedical research - and raises troubling questions about possible bias during grant reviews conducted by the U.S. National Institutes of Health (NIH).

The in-depth analysis of NIH grant data finds that black Ph.D. scientists - and not other minorities - were far less likely to receive NIH funding for a research idea than a white scientist from a similar institution with the same research record. The gap was large: A black scientist's chance of winning NIH funding was 10 percentage points lower than that of a white scientist.

The NIH-commissioned analysis, which lifts the lid on confidential grant data, may reflect a series of slight advantages white scientists accumulate over the course of a career, the authors suggest. But the gap could also result from "insidious" bias favoring whites in a peer-review system that supposedly ranks applications only on scientific merit, NIH officials say.

The findings have shaken NIH. "I was deeply dismayed," says Director Francis Collins: "This is simply unacceptable that there are differences in success that can't be explained." With NIH Deputy Director Lawrence Tabak, Collins has authored a response in Science outlining steps the agency will take to address the apparent racial disparity.

See this week's issue of Science's for the full news article on this study. And next week, Science Live will hold an online chat to discuss the study and challenges that minority and women researchers face.