A long-running debate over U.S. government-funded research that tweaks risky pathogens in ways that could make them more dangerous to humans is flaring up again. This time, at issue is whether officials should make public the work of a closed-door federal committee that weighs the risks and benefits of experiments proposed for funding by the National Institutes of Health (NIH), and in the past 2 years has greenlighted two controversial avian influenza studies.