A conflict is escalating over U.S. researchers’ use of human fetal tissue. Legislators in Wisconsin last week advanced a bill that would make it a felony for scientists working in the state to conduct studies using tissue or cells obtained from recently aborted fetuses. The measure, approved by a committee of the Wisconsin State Assembly, has drawn opposition from universities and research groups, who say it will stifle important disease studies. The bill is likely just the first of many similar state-level efforts, science policy observers predict.