U.S. health officials last week said they will allow limited clinical trials of animal-to-human transplantation to proceed, even though some researchers argue that such work poses a risk to public health and should not be permitted without further study. At a meeting on 21 and 22 January, officials from the Food and Drug Administration, the Centers for Disease Control and Prevention, and the National Institutes of Health outlined plans to allow this research to go forward under stringent safeguards that are now being finalized. They intend to impose rigorous standards to maintain disease-free donor animals, create a national registry of organ recipients, and establish both a tissue bank of samples from donor animals and recipients and a national policy advisory committee.