With almost half a billion users worldwide and with the new religion of internet-mobile just around the corner, it's a question that is starting to generate almost as much hysteria as the cell phone craze itself.
Scientists have for years been investigating suggestions that the radiation emitted by mobile phones, base stations and masts could trigger a whole medical dictionary of ailments, from dizziness to gene damage, nosebleeds to nausea, Alzheimer's to brain tumors.
Consumers meanwhile dashed out in their millions to buy the hands-free earpiece that puts a respectable distance between the mobile microwaves and the human brain.
But this week, Britain's Consumer Association warned that far from lowering the incidence of radiation on the brain, the earpiece wire could actually increase exposure threefold.
"If you're worried about levels of radiation from your mobile phone, you shouldn't rely on a hands-free set," the group said.
So what is the truth about the mobile phone hang-up?
Scientists are pursuing three broad lines of enquiry - into long-term phone use, phone-with-earpiece use, and the hazards of base stations and masts - but have yet to uncover definitive proof of harmful effects.
"One thing I wouldn't do is to have a half-hour conversation on a mobile phone because you are exposing a small area of the brain intensively and producing changes to blood flows," said Dr Alan Preece of Bristol University, who has conducted extensive research into the subject.
"With an antenna two centimeters away from the head 50-60 percent of the phone's energy goes into the head," Preece told AFP.
The Consumers' Association said this energy can cause a rise in temperature which could in turn cause headaches, sickness and dizziness. Preece was not so sure.
"We are still at an early stage and none of the research suggests there are harmful effects," he said.
As for earpieces, Preece said his research showed that hands-free kits reduced exposure to radiation to tiny levels, a contention robustly supported by the mobile industry itself.
"Tests ... have without exception shown that the absorption levels produced when using a headset are significantly less than those produced without a headset," said a spokesman for the Federation of the Electronics Industry (FEI).
Despite such assurances, politicians and pressure groups in Britain have clamored for a coordinated probe into the hazards of mobile telephony and a government-appointed task force is currently gathering evidence for a definitive report on the risks posed by the cell phone boom.
The group is looking not just at mobile devices and headsets, but at the mushrooming transmitter stations and masts that are springing up to try and meet burgeoning demand for mobile services.
"The group's remit was mobile phones but they decided that, given the public concern, they would have to look into base stations as well," said Liz Francis, a spokeswoman for the National Radiological Protection Board.
The independent expert group has already heard anecdotal and scientific evidence from dozens of witnesses.
Some have alleged that phone companies are whipping up transmitter masts overnight to avoid confrontation with a public hugely skeptical about the possible side effects of the instruments.
Others have complained of headaches, nosebleeds, ringing in ears, slurred speech, body tremors, swelling in glands, fatigue, nausea and dizziness, the group said on its website www.iegmp.org.uk