BETHESDA, MARYLAND—Fuzzy definitions, deep disagreement about risks and benefits, and an unfortunate acronym: All bedeviled an expert panel as it met here last week to examine whether the United States should fund certain risky pathogen experiments. Researchers largely praised a massive, recently released risk assessment of so-called gain-of-function (GOF) research, and a draft plan for reviewing the riskiest studies. Many had concerns about the details, however, and the meeting provided little clarity on one key issue: if and when the U.S. government will decide whether to lift a now 15-month-old moratorium on a handful of U.S.-funded virology experiments.