WHEN PRESIDENT Bush announced his policy on stem cell research in August 2001, many researchers and supporters of this promising new field were quick to criticize it. We were not. The policy permitted federal funding for stem cell research from existing cell colonies, or "lines," but not for research on lines that would be created subsequently. It wasn't an ideal arrangement, but it promised funding for this important, potentially life-saving research. And there was reason to think that the existing lines might, for a time at least, support the basic research necessary to get started. As long as the number of lines available supported the volume of research, the policy would be a reasonable -- if temporary -- balancing of the moral concerns many conservatives held about stem cell research against its potential benefits.

The policy's viability, however, now appears at an end. Researchers say they are being held back by it, and even the Bush administration concedes that the policy might no longer support all the research that scientists would like to perform on embryonic stem cells. In a recent letter to members of Congress, National Institutes of Health Director Elias A. Zerhouni said that "much of the basic research that needs to be done can be and is being supported with Federal funds under the President's policy." But he conceded that "it is also fair to say that from a purely scientific perspective more cell lines may well speed some areas of [stem cell] research." Dr. Zerhouni wrote that Mr. Bush's policy "is still predicated on his belief that taxpayer funds should not 'sanction or encourage further destruction of human embryos that have at least the potential for life.' "

The public is thus faced once again with the question of whether moral concerns over the use of human embryos should slow or frustrate research that might -- if the promise of stem cells pans out -- save many lives. The answer must be no. We do not support using federal funds to create human embryos in order to use them for research. But embryos are already being created in fertility clinics in far larger numbers than are needed for women who wish to have babies. These surplus embryos are otherwise fated to be discarded, and using them for research does not seem, in our judgment, particularly fraught with moral peril. Private funding offers some alternative, but federal research money should not continue to be limited. Mr. Bush's policy served a transitional role, but the time has come to allow researchers access to more lines.