What do brain surgeons know about cellphone safety that the rest of us don’t?

Last week, three prominent neurosurgeons told the CNN interviewer Larry King that they did not hold cellphones next to their ears. “I think the safe practice,” said Dr. Keith Black, a surgeon at Cedars-Sinai Medical Center in Los Angeles, “is to use an earpiece so you keep the microwave antenna away from your brain.”

Dr. Vini Khurana, an associate professor of neurosurgery at the Australian National University who is an outspoken critic of cellphones, said: “I use it on the speaker-phone mode. I do not hold it to my ear.” And CNN’s chief medical correspondent, Dr. Sanjay Gupta, a neurosurgeon at Emory University Hospital, said that like Dr. Black he used an earpiece.

Along with Senator Edward M. Kennedy’s recent diagnosis of a glioma, a type of tumor that critics have long associated with cellphone use, the doctors’ remarks have helped reignite a long-simmering debate about cellphones and cancer.

That supposed link has been largely dismissed by many experts, including the American Cancer Society. The theory that cellphones cause brain tumors “defies credulity,” said Dr. Eugene Flamm, chairman of neurosurgery at Montefiore Medical Center.