Surgeons have performed the first U.S. face transplant, transferring most of the visage of a corpse onto a woman who was missing most of her own face, doctors said today.

"I'm very proud and emotional today to share with you that we have finally done it," Maria Siemionow, who led the operation at the Cleveland Clinic in Ohio, said at an afternoon news conference.

Siemionow, director of plastic surgery research at the hospital, worked with a dozen specialists to rebuild the face of a woman who was missing her right eye, nose and upper jaw. The deformities left her unable to speak, smell and taste properly. The team transplanted 80 percent of the donor's face, painstakingly hooking up arteries, blood vessels, nerves, muscle and bone; the recipient still has her own chin, forehead, upper eyelids and lower lip.

Even after the news conference, many aspects of the transplant remained secret. Citing privacy, doctors refused to identify or provide any details about the recipient or how and when she was injured. They also would not identify the donor or the date of the transplant, saying only that it had occurred sometime in the past two weeks and that the recipient and donor were the same gender and race and roughly the same age.

The women were matched for blood and tissue types—the same way donors and recipients are matched for solid organ transplants—to reduce the chance that the recipient's immune system would reject the donation.

The transplant began at 5:10 A.M. and ended at 4:30 P.M., said Frank Papay, chairman of the hospital's Dermatology and Plastic Surgery Institute. The donor's cheekbone and lower eyelids were transferred to the recipient, as well as all of the muscles in the upper and mid-face, the upper lip, upper jaw (with some teeth), nose, sinuses, the facial nerve (which enables us to smile and blink) and skin.

Though swollen, the recipient is taking immune-suppressing drugs and has shown no sign of rejection (attacking the new tissue as though it were an invading germ), Siemionow said. The patient will undergo physical therapy to regain use of her face; the nerves should regenerate in three to six months, Siemionow said. She added that it will not be possible to restore vision to the woman's eye, because her optical nerves were too damaged by her injury.

The recipient was not shown a photograph of the donor and will not look like her, said Eric Kodish, a Cleveland Clinic bioethicist. Rather, the donor's soft tissue will mold itself to the recipient's bone structure, says David Staffenberg, chairman of plastic surgery at Montefiore Medical Center in the Bronx, N.Y., who was not involved in the transplant. And just like the face she was born with, he notes, the way the tissue hangs on the bone will change with time and gravity.

The new face, Staffenberg says, "winds up being somewhere in between the two, but not like the patient looked before or like the donor exactly."

Some have questioned the ethics of transplanting the face of a dead person onto that of a living one, because a failed procedure would be painful and emotionally devastating. Critics also decried the potential for abuse, of people seeking the dangerous procedure for cosmetic purposes. But the concept has gradually become more accepted. Since 2005, two partial face transplants have been performed in France, and another one took place in China. Today doctors justified the fourth, arguing that the recipient could not function in society with such an extreme deformity.

"The patient was really suffering whenever she appeared in a social situation," Siemionow said. "She was called names. Children were afraid of her—they were running away.

"The patient was brave," she added. "She was stable in facing the world, but it was very difficult for her to go out of the house."

A statement from an unidentified sibling of the recipient described the opportunity for the transplant as "overwhelming."

"We never thought for a moment that our sister would ever have a chance at a normal life again, after the trauma she endured," the sibling said. "But thanks to the wonderful person that donated her organs to help another living human being, she has another chance to live a normal life."

The hospital's Institutional Review Board first signed off on the face transplant concept in 2004. But it took another four years for physicians to map out the logistics and settle on a recipient who was up to the emotional challenge of becoming accustomed to having a new face and also up to dealing with the possibility that the operation might fail.

A dozen specialists from plastic surgery, head and neck surgery, transplant surgery, anesthesia, psychiatry, psychology, bioethics, dentistry, ophthalmology and pharmacy took part in the transplant.

Kodish said hospital staff would "do everything we can to prevent the misuse of this advancement."

"We do not think this should be used for cosmetic enhancement," Kodish said. "The face is the embodiment of personal identity. A person who's suffered trauma to the face suffers tremendously. We hope our patient will begin to smile again, begin to smell again. The relief of suffering is at the core of medical ethics and provides abundant justification for performing this procedure."