SAN DIEGO (AP) _ A 16-year-old boy who became critically ill while awaiting a donor for a lung transplant has received a lobe from each parent in what officials say was only the fifth such procedure of its kind.

James Baumgaertner and his parents were in serious condition Tuesday, said Leslie Franz, a spokeswoman for the University of California, San Diego, Medical Center.

''His lung function is very good. He now has normal lung capacity,'' said Dr. Stuart Jamieson, who led Sunday's eight-hour operation.

In all five cases, the transplant recipient suffers from cystic fibrosis, an inherited disease that attacks the lungs and kills half its victims by age 30.

James is small as a result of his illness and the transplanted lobes should grow along with him, Jamieson said.

His parents, Sharon and Philip Baumgaertner, should be released from the hospital by the weekend, Jamieson said. They have asked that their ages not be released.

James will be hospitalized for at least three weeks, he said.

James and his mother traveled to San Diego from their home in Bremerton, Wash., last year to await a lung transplant, but he became critically ill before a donor lung could be found, Jamieson said.

''We felt that we probably were running out of time,'' the doctor said.

A person's right lung naturally has three lobes and the left has two. Doctors say each lobe is believed capable of functioning as a full lung and that most donors don't notice a lobe's absence.

One lobe was taken from one lung of each parent, but doctors didn't say from which lungs the lobes were taken.

The first four transplants were performed earlier this year, said a spokeswoman for USC University Hospital in Los Angeles. All the recipients and their parents are alive.

Dr. Vaughn A. Starnes, who was involved in those operations, said about 70 percent of his lung transplant patients live three to five years.