The clear distinction between "therapeutic cloning" and human cloning is again becoming lost in reactions to reports that scientists are breaking new ground in the effort to obtain stem cells from cloned human embryos. Without an understanding of the differences between the two, policy makers and the public risk curtailing research that may lead to effective treatments and even cures for debilitating diseases. "Therapeutic cloning" is an unfortunate term that describes a method for creating stem cells to produce tissues that are less likely to be rejected by the immune system of a transplant recipient. Creating stem cells to treat humans is not the same as creating a human being.

Most important, the renewed debate on these issues lends greater support to the concept that human stem cell research that is publicly funded and conducted under the highest standards of open scientific exchange, peer review, and public oversight provides the surest and most responsible means to achieving medical breakthroughs using this technology.

Stem cells are unspecialized cells that can renew themselves indefinitely and, under the right conditions, differentiate into all types of cells. Although still in its infancy, stem cell research gives hope to millions of people suffering from diseases such as diabetes and Parkinson's, or from injuries to their spinal cords, that healthy tissue grown from stem cells can someday be used to replace their diseased or damaged tissue. There are few other treatment options on the horizon for many of these diseases.

Whenever tissue transplantation takes place, however, there is always a risk that the body's immune system will reject the new biological material, with life-threatening implications. For stem cell transplantation to be effective and broadly available, new means will be needed to overcome tissue rejection.

The term "therapeutic cloning" is a misnomer, and one that scientists don't like to use, because it implies the creation of a human clone. Instead, using a process known as somatic cell nuclear transfer, scientists place the cell nucleus of the potential transplant recipient into an egg that has had its nucleus removed. Then, in a culture dish, they try to coax the remade cell into dividing like a fertilized egg to produce stem cells, which could be harvested and grown into organs or tissues that are almost genetically identical to the transplant recipient. In theory, the body should not reject tissue derived from stem cells that are a genetic match. These techniques are far too risky and rudimentary to use for anything but potential medical therapies.

I recently chaired a committee of the National Academies' National Research Council and Institute of Medicine that examined the therapeutic potential of stem cell research. We determined that public funding of basic research on stem cells is needed given how much we don't know, the ethical issues involved, and the potential reluctance by industry to invest in efforts that could take many years to yield commercial applications. Although a few private companies are apparently willing to invest in research that may not pay off for many years, most are not. Moreover, public sponsorship would help ensure that many more scientists could pursue a variety of research questions and that their results are made widely accessible - two factors that can significantly speed progress. In addition, public funding offers greater opportunities for regulatory oversight and scrutiny of research.

Clearly, the ethical dilemmas and scientific uncertainties involved in this research need careful monitoring. Our committee recommended that the National Institutes of Health should establish a national advisory body of leading scientists, ethicists, and other stakeholders to verify that federal funding for stem cell research, including somatic cell nuclear transfer, is justified on scientific grounds and meets federal ethical guidelines. NIH has successfully dealt with controversial research in the past by setting up similar watchdog panels.

But an outright ban on somatic cell nuclear transfer research - unlike a ban on reproductive cloning - is currently unjustified on both medical and scientific grounds. Moreover, it would be tragic if such a ban were implemented simply because of confusion between these two very different types of research.

Headlines about cloned human embryos can be scary. However, if one looks beyond the words "human" and "clone" to see that scientists are not talking about a duplicate child but rather a potential medical therapy, the reality behind these headlines can be seen to be both exciting and full of hope for people with a variety of serious illnesses.