Therapeutic cloning is one of the most divisive topics in modern biology. To some, it promises a future in which damaged and diseased tissues and organs will be replaced without worrying about immune rejection. To others, the idea of creating a human embryo and culturing it for several days to obtain stem cells that would be needed to grow such grafts is morally reprehensible. The two sides have been battling it out in legislatures across the world over the past few years.

The last thing those engaged in therapeutic cloning research need, therefore, is further ethical controversy. Yet a storm seems about to break over the field's most prominent paper to date — the report in February that a group in South Korea had derived a line of embryonic stem cells from a cloned human embryo (W. S. Hwang et al. Science 303, 1669–1674; 2004). Questions are being raised about how the researchers managed to recruit so many women prepared to donate their eggs for the project. One such question is why a PhD student, who was a co-author on the paper, initially told Nature she was an egg donor but later changed her story (see pages 3 and 12).

In the context of South Korean society, it's easy to see how students involved in such a project might, with the best of intentions, want to donate their eggs. Korea is an intensely patriotic country, in which the desire to help others is deeply ingrained. The prospect of helping sick patients, and demonstrating that Korea is capable of world-leading research, would be a powerful motivating factor. In such circumstances, say bioethicists, procedures should be in place to ensure that the donors are all volunteers with no direct connection to the research. The principal investigators must now demonstrate that such safeguards were in place, and that they were rigorously applied.

Questions should also be asked of the local Institutional Review Board (IRB) that gave ethical approval for the research project. IRBs are supposed “to assure, both in advance and by periodic review, that appropriate steps are taken to protect the rights and welfare of humans participating as subjects”, according to the US Food and Drug Administration. So far, the IRB that approved the Korean cloning project has been less than forthcoming about its work.

If the air is not cleared quickly, the consequences for Korean science — and for research into therapeutic cloning internationally — could be severe. It will be a tragedy if one of the greatest scientific stories of the year ends up being remembered, in South Korea especially, as one that lost the trust of the people.