Daniel Liggons slowly was bleeding to death. Oozing blood from a stomach cancer too large for surgery, he had had 12 transfusions in 12 days. So Dr. David Fleischer, a stomach specialist at Washington's Veterans Administration Hospital, decided on a bold treatment. He peered into the 63-year-old man's stomach with a special scope, searched out bleeding patches of tumor and zapped them with a laser.

After two laser treatments, Liggons' bleeding stopped. He went home. The cancer had spread throughout his body and five days later he returned to the hospital, where he died April 16. But Fleischer's light gun had bought him precious time with his family. "He was very well pleased," said his wife Jenniebell.

For Liggons, whose death was expected, the laser was a desperate and short-term remedy. For other patients, bleeding from ulcers, stomach erosions, dilated veins in the esophagus or other causes, it can be a life-saver. The laser at the Veterans Administration Hospital is one of seven in the United States being used to stop bleeding from the upper digestive tract -- a medical emergency that strikes 150,000 Americans a year, kills 15,000 of them, and costs $500 million annually in hospital care and transfusions.

Although laser treatment still is experimental, it promises to revolutionize the treatment of these hemorhages -- whose mortality rate, unchanged for 30 years, has defied attack by other new medical and surgical therapies.

Using lasers for stomach hemorhage is commoner in Europe -- especially in Germany, where Dr. Peter Kiefhaber, who pioneered the treatment in 1973, has treated more than 500 patients. Worldwide, about 2,000 people have had laser light beamed into their stomachs via a bendable, threadlike fiber that fits through a rubber tube called an endoscope. The laser's success rate at stopping bleeding is 85-to-90 percent.

Fleischer allowed a reporter to watch the second of Liggons' laser treatments. The patient, thin and weak from cancer, lay comfortably on his side on a stretcher, in a room set up much like an operating room. In one corner stood the laser, the size and shape of a washing machine, with control dials and a lighted display panel.

With Liggons awake but sedated, and with his mouth thoroughly numbed, Fleischer maneuvered one end of what looked like a four-foot garden hose down his throat. This was the endoscope, a periscope-like instrument used by doctors to look into the esophagus and stomach.

The view through Fleischer's endoscope was like a trip into an undersea cavern: first the smooth glistening, pink tunnel of the esophagus, then the roomier, winding, coral-colored chamber of the stomach.

Suddenly, the tumor loomed like a groteque reef. Parts of it were reddish like the normal stomach wall, but instead of being smooth they were lumpy and distorted. Other areas were a dead-looking green or charcoal gray. Many sections were bright with blood.

Slowly, Fleischer trained the bright searchlight of the endoscope on a bleeding patch. An assistant said, "Ready." Fleischer pressed a pedal with his foot. There was a loud buzz and the patch of tumor seemed to melt, turned black, and instantly the bleedingd stopped.

Fleischer moved the light to another,larger patch. He aimed and shot in quick succession. The black scars blossomed, and the bleeding disappeared.

Liggons lay calmly, never in pain, for more than an hour as Fleischer sealed off one bleeding spot after another. The areas he had shot during the first treatment, five days earlier, already were healing with normal white scar tissue. There was no sign of the black burns initially produced by the laser beam, and no sign of renewed bleeding.

An assistant recorded the location of each spot and tallied the voltage it received, since there is some danger of perforating the stomach wall if too much energy hits one area.

When the treatment was safely completed, Fleischer explained how it works. In this kind of laser, krypton light "excites" a manmade crystal, raising the energy of its electrons until it gives off its own beam of light.

That beam, unlike other kinds of light, contains only one wavelength instead of many -- so it is narrow, and its energy is sharply focused. Laser light is said to differ from ordinary light the way a column of precision-marching soldiers differs from a wildly running mob.

The laser beam is bent by the clear, heat-resistant fiber, which guides it down the endoscope. When it hits stomach tissue, it is absorbed and its energy turns to heat, shrinking bleedingvessels and coagulating tissue proteins. The result is an instant scar that seals off bleeding. The doctor's eye, at the other end of the endoscope, must be shielded by a polarized lens -- otherwise, the beam's energy would scar his retina, too.

Liggons was only the third patient to be treated with the Veterans' Administration Hospital laser. The other two -- one hemorrhaging from a vein in the esophagus and one from a tear at the opening of the stomach -- also had their bleeding successfully stopped. a

Those two patients were part of a study which Fleischer, who also is an assistant professor at George Washington University Medical School, is conducting at the Veterans' Administration Hospital, which purchased the $70,000 laser.

For the study, he accepts only patients who have bled heavily in the hospital for at least four hours, despite usual treatments like pumping out the stomach and rinsing it continuously with ice water. While many people suffer minor bleeding, which stops with these measures or by itself, the patients in Fleicher's study usually are desperately ill, with little chance that their bleeding will stop spontaneously.

Because ulcers, stomach irritation, and dilated veins in the esophagus -- the commonest causes of bleeding -- are aggravated by alcohol, many of his patients are heavy drinkers, whose damaged livers make them poor surgical risks. The laser may be one of the only treatments left for them.

The patients in the study are divided into two groups. Half are treated with the laser and half are not.Whether an individual gets laser treatment is decided at random by an envelope Fleischer opens in the endoscope room.

The study is being done because, despite evidence that lasers can stop the majority of bleeding episodes, there aremany unanswered questions about the treatment's long-term effects. Therisk of immediate stomach perforation are small -- about 3 percent -- but Fleischer hopes to learn whether laster-treated patients do better in the long run: whether they permanently can avoid surgery, whether they bleed again, whether they survive longer than other patients with hemorrhages.

Lasers already have other medical roles. They are used routinely to repair detached retinas and retard damage caused by abnormal blood vessels in the eyes of diabetics. Dermatologists are removing birthmarks, cheloids and tattoos with lasers. Surgeons are using "cutting lasers" to remove growths from the vocal cords, polyps from the intestine, dead tissue from burns, and even to take out tonsils. Some gynecologists use them to cauterize suspected pre-cancerous areas on the cervix.

Fleischer emphasized that, for stomach hemorrhages, the technology of the laser is still in its infancy -- he confers with engineers after each treatment -- and that it may be several years before anyone knows whether its advantages over other forms of therapy are great enough to justify the high cost of the equipment.

"It would be really wrong for everybody to go out and buy lasers," he said. "But the potential for this being a dramatic breakthrough is really superb."

He said he is elated to be at the forefront of the field, but also frightened, because there are few ground rules about how much energy he can safely train on a patient's stomach. "I find my adrenalin level -- and the sweat level under the old armpit -- is very significant every time I do a case," he said.

He gets plenty of encouragement. "I have two sons, 5 and 3," he said. "My esteem has gone up in their eyes about 12 zillion-fold, because I have a laser like Luke Skywalker does."