CONTROVERSIES OVER stem-cell research are so last decade or so it seemed until last week.

For the last few years, the promising field of stem-cell research has focused on a technique that skirts various ethical concerns about the treatment of human embryos and the potential to clone whole human beings. But last week, U.S. and South Korean researchers announced that they went ahead with a different technique, successfully creating stem cells cloned from the normal skin cells of adults. Their work helps to open a new avenue in stem-cell research. But it also could be a step on the way to human reproductive cloning.

Some ethical worries are reasonable, but they are not enough reason to hold back this research.

Since the late 1990s, scientists have held out the prospect of extraordinary new treatments from pluripotent stem cells, which are stem cells that can grow into all sorts of different tissues at researchers urging. Scientists might be able to grow insulin-producing cells for patients with diabetes. People suffering from macular degeneration might not have to lose their sight. There is even the potential to grow whole organs, matched exactly to patients, that could replace diseased ones.

Early research often involved taking stem cells from embryos discarded during in-vitro fertilization therapy. That procedure stoked opposition from people concerned about embryo destruction during scientific experimentation. Then scientists developed a different technique for harvesting stem cells that involved reprogramming adult cells, no embryos involved.

Work on that procedure continues, but there is concern in some quarters that it will not reliably and uniformly produce usable stem cells. So other scientists have been working on something called somatic cell nuclear transfer, which involves taking the nucleus out of a human egg and replacing it with the nucleus from an adult cell. Last weeks announcement came from researchers who had refined the nuclear transfer process and achieved the results they were looking for pluripotent human stem cells.

The procedure is not perfect. It took a lot of eggs to record a few successes. Moreover, it is the sort of technique scientists would use if they were trying to engage in reproductive cloning creating fully formed human beings who are exact genetic copies of other human beings. The question is whether researchers who arent interested in reproductive cloning should be barred from refining the nuclear transfer process lest a rogue scientist decides to try Xeroxing people.

Wed say that they should not be restricted if the method may advance the search for bona fide stem-cell therapies. The potential to directly and significantly reduce human suffering is too great to close off every line of research but the one that carries zero controversy. There is, moreover, a clear ethical distinction between cloning a humans cells in order to redeploy them in medical treatment and growing a genetic copy of a human being. As long as scientists do not cross ethical lines much farther from where they are now lines that Congress could write into federal law researchers should have the flexibility to go in whichever direction is scientifically useful.

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In stem-cell research, health benefits outweigh the risks ...