For nearly 15 years, Kim and Walt Best have been paying about $200 a year to keep nine embryos stored in a freezer at a fertility clinic at Duke University -- embryos that they no longer need, because they are finished having children but that Ms. Best cannot bear to destroy, donate for research or give away to another couple.

The embryos were created by in vitro fertilization, which gave the Bests a set of twins, now 14 years old.

Although the couple, who live in Brentwood, Tenn., have known for years that they wanted no more children, deciding what to do with the extra embryos has been a dilemma. He would have them discarded; she cannot.

"There is no easy answer," said Ms. Best, a nurse. "I can't look at my twins and not wonder sometimes what the other nine would be like. I will keep them frozen for now. I will search in my heart."

At least 400,000 embryos are frozen at clinics around the country, with more being added every day, and many people who are done having children are finding it harder than they had ever expected to decide the fate of those embryos.

A new survey of 1,020 fertility patients at nine clinics reveals more than a little discontent with the most common options offered by the clinics. The survey, in which Ms. Best took part, is being published on Thursday in the journal Fertility and Sterility.

Among patients who wanted no more children, 53 percent did not want to donate their embryos to other couples, mostly because they did not want someone else bringing up their children, or did not want their own children to worry about encountering an unknown sibling someday.

Forty-three percent did not want the embryos discarded. About 66 percent said they would be likely to donate the embryos for research, but that option was available at only four of the nine clinics in the survey. Twenty percent said they were likely to keep the embryos frozen forever.

Embryos can remain viable for a decade or more if they are frozen properly but not all of them survive when they are thawed.

Smaller numbers of patients wished for solutions that typically are not offered. Among them were holding a small ceremony during the thawing and disposal of the embryos, or having them placed in the woman's body at a time in her cycle when she would probably not become pregnant, so that they would die naturally.

The message from the survey is that patients need more information, earlier in the in vitro process, to let them know that frozen embryos may result and that deciding what to do with them in the future "may be difficult in ways you don't anticipate," said Dr. Anne Drapkin Lyerly, the first author of the study and a bioethicist and associate professor of obstetrics and gynecology at Duke University.

Dr. Lyerly also said discussions about the embryos should be "revisited, and not happen just at the time of embryo freezing, because people's goals and their way of thinking about embryos change as time passes and they go through infertility treatment."

Many couples are so desperate to have a child that when eggs are fertilized in the clinic, they want to create as many embryos as possible, to maximize their chances, Dr. Lyerly said. At that time, the notion that there could be too many embryos may seem unimaginable. (In Italy, fertility clinics are not allowed to create more embryos than can be implanted in the uterus at one time, specifically to avoid the ethical quandary posed by frozen embryos.)

In a previous study by Dr. Lyerly, women expressed wide-ranging views about embryos: one called them "just another laboratory specimen," but another said a freezer full of embryos was "like an orphanage."

Dr. Mark V. Sauer, the director of the Center for Women's Reproductive Care at Columbia University Medical Center in Manhattan, said: "It's a huge issue. And the wife and husband may not be on the same page."

Some people pay storage fees for years and years, Dr. Sauer said. Others stop paying and disappear, leaving the clinic to decide whether to maintain the embryos free or to get rid of them.

"They would rather have you pull the trigger on the embryos," Dr. Sauer said. "It's like, 'I don't want another baby, but I don't have it in me; I have too much guilt to tell you what to do, to have them discarded.' "

A few patients have asked that extra embryos be given to them, and he cooperates, Dr. Sauer said, adding, "I don't know if they take them home and bury them."

Federal and state regulations have made it increasingly difficult for those who want to donate to other couples, requiring that donors come back to the clinic to be screened for infectious diseases, sometimes at their own expense, Dr. Sauer said.

"It's partly reflected in the attitude of the clinics," he said, explaining that he does not even suggest that people give embryos to other couples anymore, whereas 10 years ago many patients did donate.

Ms. Best said her nine embryos "have the potential to become beautiful people."

The thought of giving them up for research "conjures all sorts of horrors, from Frankenstein to the Holocaust," she said, adding that destroying them would be preferable.

Her teenage daughter favors letting another couple adopt the embryos, but, Ms. Best said, she would worry too much about "what kind of parents they were with, what kind of life they had."

Another survey participant, Lynnelle Fowler McDonald, a case manager for a nonprofit social service agency in Durham, N.C., has one embryo frozen at Duke, all that is left of three failed efforts at the fertility clinic.

Given the physical and emotional stress, and the expense of in vitro fertilization, Ms. McDonald said she did not know whether she and her husband could go through it again. But to get rid of that last embryo would be final; it would mean they were giving up.

"There is still, in the back of my mind, this hope," she said.

At the Genetics and IVF Institute in Fairfax, Va., Andrew Dorfmann, the chief embryologist, said many patients were genuinely torn about what to do with extra embryos, and that a few had asked to be present to say a prayer when their embryos were thawed and destroyed.

Jacqueline Betancourt, a marketing analyst with a software company who took part in the survey, said she and her husband donated their embryos at Duke "to science, whatever that means." It was important to them that the embryos were not just going to be discarded without any use being made of them.

Ms. Betancourt, who has two sons, said: "We didn't ask many questions. We were just comfortable with the idea that they weren't going to be destroyed. We didn't see the point in destroying something that could be useful to science, to other people, to helping other people."

Ms. Betancourt said she wished there had been more discussion about the extra embryos early in the process. If she had known more, she said, she might have considered creating fewer embryos in the first place.