The Cleveland Clinic said it is the first institution where the review board has approved the procedure, after 10 months debating medical, ethical and psychological issues for the risky operation. Several independent medical teams around the world also are pursuing the procedure.

"We are at this point ready to begin screening patients," said Dr. Maria Siemionow, the hospital's director of plastic surgery research and training in microscopic surgery, who advocated the procedure.

Finding the appropriate donor might be more difficult than a patient, she said.

"It may not happen in six months or a year," she said. "It may not happen in our life, or it may happen sooner than you expect."

Siemionow said she will tell patients the chance is as high as 50 percent that the transplant will fail because of tissue rejection or other complications.

Finding the first patient could take up to two years, said Dr. James Zins, chairman of plastic surgery at the Clinic.

Face transplants have stirred controversy among doctors and ethicists worldwide.

A central question is whether patients should be subjected to risks of transplant failure and life-threatening complications from anti-rejection drugs, for an operation that is not life-or-death. Critics argue that those risks are not well understood.

Siemionow, 54, directed hundreds of published studies involving microcirculation and the successful transplantation of faces, limbs and other tissues in laboratory rats.

Siemionow said she wants to start with a relatively simple procedure that involves transplanting only the skin and underlying fat. The patient's muscles shape the face, so the patient would not take on the appearance of the donor.

Informed-consent agreements will be given to patients and donor families caution patients that the transplant does not guarantee they will ever look "normal" and that the transplant could possibly worsen their appearance and ability to move their face.

Despite refinements in reconstructive surgery, results "following major trauma, burns and tumor resections has been, at best, mediocre," Dr. Graham Lister, a retired professor of plastic surgery and a mentor of Siemionow's, wrote on her behalf to the Clinic review board.