ASHINGTON, July 11 — When the United States' first test tube baby was born in 1981, the Jones Institute for Reproductive Medicine, where she was conceived, found itself at the center of an intense debate over whether scientists should tamper with the beginnings of human life.

Now, by dipping into the tumultuous waters of human embryonic stem cell research, the Jones Institute, a fertility clinic in Norfolk, Va., is reliving those times.

On Tuesday, the institute's scientists announced that they had mixed eggs and sperm for the express purpose of extracting stem cells from the resulting embryos. Today, amid criticism of the experiment, the clinic's 90-year-old co-founder and namesake stood behind the work.

"The attitude of this institute," Dr. Howard W. Jones Jr. said, "has been that if we believe something is for the benefit of all and if we are persuaded after mature consideration that it is ethically correct, we are not afraid to go ahead."

Others in the world of in vitro fertilization are not quite so bold. Clinics have tens of thousands of embryos in frozen storage that could potentially be used for research, and a handful have provided embryos to scientists who study stem cells.

But the Jones Institute, as far as experts know, is the only fertility clinic in the nation whose scientists have themselves tried to derive stem cells.

"I'm in an academic medical center and there are researchers right next door who could benefit from us developing stem cell lines," said Dr. James A. Grifo, a reproductive endocrinologist at New York University School of Medicine. But, he said, "We currently haven't done it because we are afraid of the fallout."

Embryonic stem cells are primordial cells that have the potential to grow into any cell or tissue in the body, and so scientists say they hold promise for repairing and replacing damaged organs.

The research draws opposition from religious conservatives, as well as the Roman Catholic Church, because it results in the destruction of embryos, microscopic clusters of cells that some regard as nascent human life.

The Jones Institute experiment was startling, even to some proponents of stem cell science, because it broke a medical taboo against mixing eggs and sperm to create fresh embryos expressly for research.

"What they did today is sort of true to their character," John Fletcher, professor emeritus of bioethics at the University of Virginia, said of the institute. "They have always played their cards close to their vest."

And it inflamed the continuing debate, coming just as President Bush is considering whether to permit taxpayers to finance studies of stem cells derived from frozen embryos that would otherwise be discarded. A decision is expected this month.

Mr. Bush's spokesman, Ari Fleischer, said, "The president views this as a reminder that this is not a simple matter."

Mr. Fleischer described the experiment as "a perfect illustration of the deep complexities" of the debate.

On Capitol Hill, legislators on both sides said they would use the Jones Institute study to try to sway the president.

Senator Sam Brownback, the Kansas Republican who is opposed to the research, said providing taxpayer money for research on frozen embryos would only serve to create "an encouraging environment" for studies such as the Jones Institute's, which he called "shocking and completely wrong."

Senator Arlen Specter, the Pennsylvania Republican who favors the research, said the study demonstrated the need for federal financing, because if the government paid for the research the government could regulate it. And, Mr. Specter said, Congress should take up the matter regardless of Mr. Bush's decision. The scientist who conducted the experiment, Dr. Gary Hodgen, was not available to be interviewed today.

Dr. Hodgen spent more than a decade at the National Institutes of Health, and was head of the pregnancy research branch at the National Institute on Child Health and Human Development, where he studied ovarian physiology in monkeys during the 1970's.

Dr. Hodgen left the health institutes in 1984, frustrated that a federal ban on research involving human embryos was impeding his work.

At the time, he recalled in a 1997 interview, he wanted to experiment with screening embryos for hereditary diseases, so that couples carrying the genes for those diseases might have healthy children. Years later, he performed the screening at the Jones Institute.

In that interview, Dr. Hodgen said he had developed his own "double- based litmus test" of two questions that he always asked himself before conducting an experiment: Will it meet an unmet need of patients and families? Will it help society?

"Each person," Dr. Hodgen said then, "must search their own soul for what they spend their time doing."

Category: 31. Stem Cells