As technology continues to advance, countries must decide how they will deal with the issue of human cloning for reproduction or research. So far, several nations have placed strong restrictions on therapeutic cloning; others are moving towards such restrictions, and a few have staked out positions in favour of therapeutic cloning. After months of acrimonious debate, the United States must now decide what it will do.

All legislators can agree that it would be wrong now to make a walking, talking, real-life human clone. The National Academy of Sciences also supports that position. But its Institute of Medicine has rightly said that its objections to the safety of reproductive cloning do not apply to research cloning. Indeed, some scientists say that research cloning could yield stem cells that could be used to grow therapeutic tissues for patients with diseases such as Parkinson's. They also say that studying stem cells made from the cells of diseased patients could help us understand why people with the same genetic make-up get sick or stay well.

Opponents of research cloning say there is no proof that it will yield any cures. They also say that adult stem cells are more promising and less controversial. They have gained Congressional and public support by tapping into widespread fears about biotechnology, which some worry is careening quickly down a slippery slope towards the commodification of the human species. But such fears do not represent a sensible basis for a ban on research cloning, which is likely to give insights into the processes that underlie a host of debilitating diseases (see Nature 414, 567; 2001).

The Senate is now moving towards a showdown on this issue. Two bills have been introduced. Senator Sam Brownback (Republican, Kansas) introduced a bill that would ban cloning for any purpose. His rivals, led by Senator Dianne Feinstein, (Democrat, California), have introduced competing legislation that would allow scientists to clone embryos for research. And senators eager to air their views on the issue are calling for a vote on the matter in the next few weeks. Brownback is said to have nearly 50 supporters, but for technical reasons a bill is unlikely to be passed unless 60 senators support it.

Advocates of therapeutic cloning have outlined scenarios that would make the Senate more likely to pass a bill that would allow research cloning, such as amending the Brownback bill to allow research. In this way, senators could save face by simultaneously voting for Brownback and for research.

However, any bill that does pass the Senate must be reconciled with the House bill in a conference. The Brownback bill is virtually identical to a House cloning ban that was passed last July. So it would speed through the conference committee. But Senate and House negotiators are unlikely to compromise if the Senate votes to allow therapeutic cloning. So the result of this month's Senate debate is likely to be either that President Bush signs a bill that bans cloning for any purpose, or that he does not sign any cloning bill at all. The issue could also spill over into the appropriations process this autumn, when senators try to force rules through the Congress by attaching them to necessary spending bills.

The Congress has strongly supported the National Institutes of Health in recent years because it wants the United States to be a world leader in biomedical research. The Senate should continue its strong support of biomedical science, and act in the national interest, by refusing to pass a ban on research cloning.