Tough new rules on ethics and on competing interests have caused four top researchers at the US National Institutes of Health (NIH) to quit and a prospective new head of one of the institutes to reconsider taking up the position. Meanwhile, the director of the NIH, Elias Zerhouni, told a Senate committee on 6 April that the rules had had a “deleterious impact” on the institutes and that he would consider changes.

The most senior of the top researchers to leave is James Battey, chairman of the NIH's stem cell task force and head of its National Institute on Deafness and Other Communication Disorders, who will retire in September. He has applied to be president of the new California Institute for …