With the practiced elan of an astronaut donning his space helmet before a launching, Neil Greenberg pulls a capsule the size and shape of a large breadbox over his head and turns it on.
Mr. Greenberg is the proprietor of Natural Image, what is called a nonsurgical hair restoration salon, in Plymouth Meeting, Pa. ''Don't worry, this is completely safe,'' he says as his chin and mouth glow red beneath the device's rim. ''There's virtually no sensation at all.''
This is not to say that nothing is happening. Within the hood of his Laser Tek 5000 Mr. Greenberg's head is being bombarded by the light from 50 laser diodes to try to bring about a metamorphosis that defies known medical science. Indeed, Mr. Greenberg said, the Laser Tek 5000 can do what doctors, folk healers and sorcerers have failed to do for centuries — restore hair to a balding man's scalp.
The key is a process called photobiostimulation, said Lisa Cutler, Mr. Greenberg's colleague and the proprietor of the Natural Image studio in Cherry Hill, N.J., where this demonstration took place. ''Technically, it won't bring back follicles that have died,'' she said. ''But it will rejuvenate those that are on their way out and make the rest of your hair thicker, softer and more luxuriant.''
It usually takes two sessions a week for three to six months for clients to see whether they have new growth, she said, and they may pay up to $2,800 at her salon or $3,500 at Mr. Greenberg's. This price includes a monthly allotment of dexpanthenol, a sebum (oily scalp) control agent; a nonirritant shampoo; minoxidil; and an ''herbal DHT-killer'' intended to neutralize dihydro-testosterone (DHT) in the manner of Propecia.
''That's a $60-a-month value,'' Mr. Greenberg said. In a testimonial video that Ms. Cutler shows, . ''I was 18 when I noticed my hair was receding at the temples and getting thin in front,'' he said. He considered a transplant, but was advised he was too young. He arrived at Ms. Cutler's salon shortly after her Laser Tek arrived.
Within a few weeks, he said, he began to see results. ''I see a big difference when I look at family photos taken a few years ago,'' he said. ''From what I've read on the Net it will take three to seven years to get all my hair back. Then I'll have to come in just once a month for maintenance.''
Laser treatment can also be performed in the home, according to David Michaels, managing director of Lexington International of Boca Raton, Fla. His company manufactures the HairMax LaserComb, a hand-held laser device the size of a hairbrush that sells for $645. ''The advantage of the HairMax is, you pay one low price instead of paying for repeat visits to a clinic and you do it in the comfort of your own home,'' he said. ''All you have to do is brush your hair slowly with the HairMax for 15 minutes, three times a week.''
Mr. Michaels says his device has been ''cleared'' by the Food and Drug Administration, which has indeed pronounced it safe, though it has made no determination that it works.
Doctors question the benefits of laser hair therapy. Dr. Sandy Tsao, a dermatologist at Massachusetts General Hospital and an instructor in dermatology at Harvard Medical School, says skepticism about laser hair restoration prevails.
''We've been using lasers for years, but mostly to remove hair,'' she said. ''We've seen that sometimes, when we use inadequate energy to use lasers to remove hair, hair will grow. So now the theory is, if you can stimulate the follicle to reactivate hair cells, you can get new hair growth. This is a huge leap of faith. In those cases where it happens, it's a random hit. It took a long time to learn how to kill a follicle; it's going to take a lot more time to learn how to revive one.''
While the medical establishment is dubious, the news media have been intrigued.
In one continuing TV study first aired in November 2004, ''Dateline NBC'' presented five balding men, all patients of Dr. Alan Bauman of Boca Raton, six months after they had each undergone five different forms of treatment.
The five were examined by Dr. Paolo Romanelli, an assistant professor of dermatology at the University of Miami. The results of a Propecia and minoxidil program were proclaimed ''fair to moderate,'' while Propecia alone produced ''moderate growth with good results around the bitemporal area.'' Viviscal, a marine-extract-based pill, produced no visible growth; the results of a transplant performed by Dr. Bauman were ''good growth''; and the HairMax results were ''substantial'' with new follicles growing on the subject's crown.
A subsequent broadcast, to report on results 12 months after, is planned. In one sense, Dr. Bauman said, the study was a success. ''It was shown to nine million people,'' he said. But, he added, ''It wasn't science — it was made for TV.''
''I've been using lasers since 1999, longer than anyone I know,'' he said. ''It's a nice, nonsurgical, nonpharmaceutical way to promote hair growth.'' He also sells the HairMax to patients who can't make twice-weekly visits to his office. But he's realistic about its limitations. ''Other treatments may be, by themselves, far more effective than lasers against hair loss.'' But lasers, he said, are easier to sell. ''They've got more sizzle.''
Lasers as hair restorers may already be passe, according to Dr. Roy Geronemus, director of the Laser and Skin Surgery Center of New York and president of the American Society for Laser Medicine and Surgery.
A new technology may soon replace lasers in many cosmetic and medical applications, he said. ''It uses light-emitting diodes not unlike the L.E.D. in your TV remote, and it's been shown to have a positive effect on tissue,'' Dr. Geronemus said. ''This is the wave of the future.''