Practically nobody even bothers to confirm the diagnosis of most peptic ulcers these days. Treatment is just too simple.

Says Dr. William Stern, a gastroenterologist at Shady Grove Adventist Hospital in Montgomery County, "You have a pain in your stomach that is temporarily eased by food. You go to your family doctor and likely as not, without even checking, they'll send you home with a prescription for Tagamet or Zantac." Usually, in a few weeks the pain from what may or may not have been a peptic ulcer is gone and probably will not return.

An ulcer is a sore in the lining of the stomach or small intestine. For most of the 15 million to 20 million sufferers a year, they are a minor inconvenience, thanks to those new drugs, which prevent production of irritating stomach acid. Still, occasionally ulcers can be temporarily disabling, as was the case with William Sessions, the new FBI director, who was hospitalized last week for the second time. Sessions had what doctors call an "abrasion," the beginnings of an ulcer, in the duodenum.

And although the condition is easily treated, an estimated 8,000 Americans a year still die from ulcer complications.

Ulcers of the stomach (gastric ulcers) or ulcers of the upper part of the small intestine (duodenal ulcers) may be dangerous without being particularly painful or, in fact, without any obvious symptoms until loss of blood causes weakness or unconsciousness. The serious complications occur as a result of bleeding or perforation, when the sore eats through the wall of the stomach or lining of the intestine.

People with ulcers are no longer restricted to bland diets and tend to do well on current medications. Even better treatments are close at hand, Stern says.

According to Martin Hassner of the American Digestive Disease Association, only 15 percent of ulcer cases these days are ever even seen by gastroenterologists. The discovery of cimetadine (Tagamet) has, for the most part, turned this common and potentially deadly disorder into something almost routinely curable by an internist or family practitioner. It's one of the minor medical miracles of our time, one that has quietly mushroomed, mostly over the last five or six years.

Drug companies have noticed, of course. Tagamet, first marketed in the late 1970s by SmithKline & French, is the best-selling prescription drug in history. It reached cumulative sales of $1 billion dollars in 1986, and, despite some competition from other similar drugs, it is still the most frequently prescribed drug in this country. (The number two drug is Zantac, or ranitidine hydrochloride, an anti-ulcer drug manufactured by Glaxo and part of the same family of drugs as Tagamet.)

While the number of ulcer victims has not changed appreciably in the last three decades, the ratio of men to women has changed radically: From a ratio of approximately 20 male patients to one female patient, it is now considered about half and half. Initially, scientists attributed increased incidence of ulcers in women to the women's movement -- more women under more stress -- but now most believe the increase is more likely linked to the fact that more women smoke cigarettes. Smokers are at increased risk for duodenal ulcers, and those with ulcers who continue to smoke tend to take longer to heal and are more likely to have complications and recurrences.

In the 1950s, peptic ulcers were mostly treated with something called the Sippy diet -- named for the physician who devised it, not because it was sipped or insipid (although it was both). It consisted mostly of cream, milk, milk products like cottage cheese and other bland nourishment. As it turned out, it did at least as much harm as good. According to gastroenterologist Stern, "We've gotten away from that because we found that the calcium in milk actually stimulates the secretion of acid."

For years, the medical consensus projected the image of an "ulcer personality," something akin to today's Type A heart attack personality -- someone who was driving and driven, workaholic and anxious. People didn't talk about stress per se in the 1950s and '60s, but the best thinking laid ulcers almost exclusively at the door of what is known today as stress reactivity. It is a concept that, slightly modified, is reemerging today because of new discoveries about the neurobiology of the brain and the actions of brain chemicals in other parts of the body, including the stomach and the rest of the gastrointestinal tract.

Until the late 1970s, if the Sippy diet didn't work, as it usually did not, there was the option of surgery. Mostly this involved excising half of the stomach, eliminating the portion that secreted the stomach acids. This surgery is rarely performed today. The medical community was pretty sure that stomach acids were somehow involved with ulcers, and British doctors kept insisting that cigarettes were bad for the ulcer victim. (American doctors disagreed on the latter in those days but have come around. According to one expert, duodenal ulcers are 70 times more likely to occur in smokers than nonsmokers.)

But even though by the mid-1960s the researchers were more or less on the right track in identifying things that were bad news for ulcer sufferers, they hadn't gotten very far in finding things that healed. For example, one 1960s development that caused a brief flurry of excitement was the use of balloons containing alcohol at below-zero temperatures. The balloon was placed in the patient's stomach via the throat and kept there for about an hour. It was said to cause "a sharp decrease in the flow of stomach acids," a 1963 Washington Post article said.

Another technique reported on in 1967 involved the use of a Russian "electrosone," in which 20 daily treatments of electric pulses applied to the head allegedly cured a variety of ills, including ulcers. None of these worked.

One physician recommended 14 hours a day of sleep for ulcer patients, and back in 1943 one doctor injected histamine, a substance found in many tissues, into the stomach of a patient and reported good results. Curiously enough, the drugs that revolutionized ulcer treatment -- Tagamet and the related drugs -- are types of antihistamines. Histamine acts differently in the gut than it does, for example, in the nose on a high-pollen day.

In the gastrointestinal tract, histamine causes the secretion of the acids in the stomach -- pepsin and hydrochloric acid. Tagamet and its ilk prevent the histamine from exciting the acid-producing cells.

Other breakthrough drugs under development include some that will enhance the protective lining of the stomach and duodenum and will even permit ulcer victims to take aspirin and other anti-inflammatory drugs that now are known to cause ulcers in some people.

Other research has suggested that some ulcers are caused by a bacterium called campylobacter, but this is still undergoing further investigation.

Research involving the activity of brain-cell messengers -- neurotransmitters -- in the intestinal tract is also showing promise and indicating a possible mechanism by which external events, including stress, help cause a peptic ulcer.