The surgeon peers through a double-barreled microscope, taking aim at the tissue he wants to destroy. He brings his target into focus and calls out orders to his technician, who resets the command buttons. "Give me a 100 millisecond repeating pulse," the surgeon says.

Checking his line of sight once more on the video monitor, the surgeon steps on a foot pedal and -- zap! An invisible beam of laser light burns a hole in the tissue just where he wanted it to.

In this case, the tissue is the skin of a tomato. Here at the Park Hyatt Hotel in Washington, where 250 gynecologists assembled last month for a four-day course on lasers in gynecological surgery, skinned tomatoes and seared hunks of beef tongue are evidence that the gynecologists are getting some experience with machines that could revolutionize their office and hospital practices -- machines that control the beams of light known as lasers.

"Many surgeons are afraid of lasers," says Dr. John Marlow, course coordinator and director of continuing education at the Columbia Hospital for Women. "They've gotten the idea that a laser is some sort of death ray." An estimated 20 to 30 percent of the nation's 30,000 gynecologists are trained in laser technology.

"But a laser isn't a magic light," he adds. "It's just a tool. And it's only as good as the surgeon who uses it."

Laser light -- the name is an acronym for light amplification by stimulated emission of radiation -- is a concentrated beam of light that directs heat to one tiny spot. The light beam is so precise, says Marlow, that it can be used to burn 12 separate holes into a single red blood cell.

Because the laser is so accurate and because it dramatically limits bleeding, it is being used increasingly to vaporize genital warts, take tissue samples and remove precancerous cells.

Two kinds of lasers now have approval from the Food and Drug Administration (FDA) for use in gynecological surgery: carbon dioxide (CO2) and Nd:YAG (known simply as YAG, for the three elements the its light is derived from: yttrium, aluminum and garnet).

A third type of laser, KTP (derived from potassium, titanyl and phosphate), was developed in 1981 and is under investigation for several gynecological procedures. "But KTP has not even been approved yet," except for endometriosis surgery, says Dr. Jennie Ann Freiman, director of the gynecological laser center at Lenox Hill Hospital in New York, "and already it has been supplanted by the copper vapor laser," which she says promises to be even more versatile.

The FDA has approved lasers for several uses in gynecology. The CO2 laser is approved for most procedures involving the lower reproductive tract -- vulva, vagina and cervix. This includes removal of papillomavirus warts of the vulva and cervix; removal of any abnormal cell growth of these regions; and cone biopsy, taking a piece of tissue from the cervix to examine it after an abnormal Pap smear.

The CO2 and YAG lasers also are used in certain abdominal procedures. To enter the abdomen, the laser beam is directed through a laparoscope, a rigid tube inserted through an incision in a woman's navel. Tiny fiber optic tubes may also be threaded through the laparoscope, both to allow the surgeon to peer into the abdomen and to carry YAG laser beams (though not the CO2 beam, which flows through the air) along its filaments.

Abdominal uses of the CO2 laser involve surgery for infertility, such as repair of scarred Fallopian tubes and removal of endometriosis -- bits of uterine lining scattered throughout the abdomen.

The YAG laser, which works by coagulating rather than vaporizing tissue, is used for intrauterine procedures because of its ability to travel along fiber optic tubes. The tubes can be directed right into the uterus through a hysteroscope inserted through the vagina. The FDA allows the YAG laser to be used for removal of fibroid tumors of the uterus -- a myomectomy; for removal of cancerous growths inside the uterus, and for surgery to stop excessive menstrual bleeding.

This last condition -- menorrhagia -- is common in women approaching menopause and is often treated with a total hysterectomy. Laser treatment could make removal of the uterus unnecessary by simply sealing off the cells of the uterine lining that account for the excess bleeding. Some 40 percent of women who receive hysterectomies could theoretically be treated with YAG laser surgery.

"As the technology improves," says Freiman, "I think laser surgery eventually is going to replace regular scalpel surgery."

For simple, gynecological procedures, the laser already is becoming the tool of choice. Marlow says vulvectomy, or removal of the vulva, was "standard practice" in the treatment of intra-epithelial (non-invasive) cancer until five or six years ago. It has been replaced almost altogether by laser treatment, which leaves most of the vulva intact.

For genital warts caused by human papillomavirus, lasers are beginning to rival electrical methods of removal -- either through freezing or burning of the lesions -- in efficacy and speed of recovery. "There's some controversy here, primarily over the expense of the laser method," Marlow says. But in his experience laser treatment of warts is quicker, the recovery time shorter and the relapse rate better than any other method.

The cone biopsy, in which a cone-shaped section of the cervix is removed for study following an abnormal Pap smear, is also simplified when done with a laser, he says. The CO2 laser destroys a clearly demarcated area of tissue as it cuts away the cone, meaning less damage to nearby tissue, less bleeding -- the laser seals off blood vessels as it destroys them -- and quicker recovery.

"When a laser is used for a cone biopsy, the average blood loss is eight to 10 cc's of blood -- less than 2 teaspoons," Marlow says. "Using a knife, the average blood loss is 150 cc's, or two thirds of a cup." One of the laser's benefits in gynecological surgery -- that it actually vaporizes tissue, leaving no dead tissue behind -- is also one of its hazards. The CO2 laser, as it burns through tissue, creates a great deal of smoke, and that smoke can be toxic.

"We consider that smoke to be hazardous, just like cigarette smoke," says Marlow. It contains hydrocarbons, a byproduct of the heating of carbon dioxide, as well as particles of virus from the lesion being burned away. At the very least, the smoke can interfere with the surgeon's field of vision; at the most, it can irritate the airways of physicians and spread contagious disease.

Today, operating room laser machines come equipped with smoke evacuators that draw away the so-called "laser plume" almost as quickly as it is generated. Still, laser surgeons occasionally develop pneumonitis, inflammation of the airways, and even warts in the nasotrachial and bronchial tracts after removing human papillomavirus warts.

"The smoke contains viral particles and viral DNA," says Freiman, "and presents a real occupational hazard. There's also concern about the surgeons' developing malignancy" because the human papillomavirus has been associated with certain cancers. But Freiman says she has not yet heard of any such cases.

Another occupational hazard to laser operators is eye damage. When laser light bounces off the tissue, a phenomenon called backscatter, it can reflect back to the surgeon's eyes and damage the retina. For this reason, all laser operators must wear special goggles that block the part of the light spectrum that contains the laser rays. Microscopes used in microsurgery involving lasers already have a protective shield in the eyepiece.

There's also the hazard to the patient that, in the hands of an unskilled surgeon, pieces of the bowel or chest can accidentally be burned by a misguided beam. This brings up the issue of control. Who's to stop untrained surgeons from including this powerful tool in their black bags?

In hospitals, credentialing committees can limit laser surgery privileges to surgeons who have completed a postgraduate course in the basics of laser technique (which usually costs about $900), as well as a preceptorship of a few weeks or months with an experienced laser surgeon. Since laser machines are available in office models -- costing as little as $17,000, compared to $80,000 to $100,000 for a top-of-the-line model -- some concern exists that gynecologists can use them in their offices without the training or oversight required by hospitals.

"Overuse is always a danger with a new technology," says Marlow. "In addition, he says, the move away from obstetrics on the part of many gynecologists, fueled by soaring malpractice premiums for those who deliver babies, has left many gynecologists looking for new skills to market.

But with lasers, he says, "I think a more important problem is that not enough gynecologists are fully trained in the technique, so they're not applying something that would be helpful to their patients."

Freiman has found resistance to lasers among older gynecologists, who like the feel of a scalpel in their hands and a direct line of sight to the tissue they're cutting. The hand-eye coordination required in operating through a microscope, using a joy stick or other no-touch means of directing the light beam is something that takes a lot of adjustment.

"I think the younger generation of surgeons coming up will have a much easier time of it," Marlow says. "The ones who have been raised at the video arcades."

Robin Marantz Henig is a free-lance writer in Washington.