In 1939, long before high-tech drugs came along to treat the chest pain known as angina, an Italian surgeon named Fieschi devised a simple technique. Reasoning that increased blood flow to the heart would ease his patients' pain, he made tiny incisions in their chests and tied knots in two arteries. The results were spectacular. Three quarters of all patients improved." One third were cured.

Two decades later, the National Institutes of Health paid a young cardiologist in Seattle, Dr. Leonard A. Cobb, to conduct a novel test of the Fieschi technique. Cobb operated on 17 patients. Eight had their arteries tied; the other nine got incisions, nothing more. In 1959, the New England Journal of Medicine published his findings: The phony operations worked just as well as the real thing.

That was beginning of the end of the procedure, known as internal mammary artery ligation; within two years, it became a footnote in the medical history texts. It was also the beginning and the end, apparently, for sham surgery in this country. By the early 1970s, an ethics revolution had transformed human experiments, and the idea of surgery as placebo was unthinkable.

Unthinkable until now. Sham surgery is on the rise, to the horror of some doctors who say it is immoral and to the delight of others who say it is time to apply the same rigorous scientific standards to surgery as to the rest of the medical profession. And with it comes a host of thorny questions.

The results of the first sham brain surgery study were reported last week in Toronto by a team of neurologists. Forty people with Parkinson's disease participated. Each had neurosurgery: four tiny holes, drilled through the forehead into the skull. But only half got the injections of fetal cells that might have repaired their damaged brains; the other half got nothing. One year later, three members of the placebo group said their symptoms had improved.

The study has drawn praise from officials at the National Institutes of Health, who paid for it, but also criticism from other quarters. "A placebo is truly inert and harmless," said Dr. Arthur Caplan, the bioethicist at the University of Pennsylvania. "This is not a placebo. It is a phony surgical operation."

Despite Caplan's protests, there are similar studies underway, in part because the federal government is requiring them and in part because new, less invasive, surgical methods make them feasible. Two other groups researching Parkinson's are running sham neurosurgery tests. A Rhode Island biotech company, Cytotherapeutics, is using phony operations to study a treatment for cancer pain that inserts analgesic capsules into the fluid at the base of the spine. In Houston, the Department of Veterans' Affairs is sponsoring a program to see if arthroscopic surgery, a common treatment for knee injuries, works for osteoarthritis.

"If we so well accept a placebo in medicine trials, drug trials, why don't we accept it in surgery trials?" asked Dr. Nelda Wray, chief of general medicine at the VA Hospital in Houston. "My hope is for us to critically think about the risk of the placebo, and if we can reduce it, we should think about doing placebo trials before we disseminate surgical procedures."

Weighing the risks and benefits, however, is not a simple task. The 180 patients in Dr. Wray's study, for instance, will be placed under general anesthesia. Dr. Baruch Brody, an ethicist at Baylor University who advised Dr. Wray, said he approved the design because the risks of sedation have dropped substantially in recent years.

The placebo effect in medicine is well-documented. The word is Latin, from the Catholic prayer for the dead, meaning "I shall please." In centuries past, doctors used placebos to placate problem patients. "You gave them something to send them away happy," said Anne Harrington, a medical historian at Harvard University. Experts estimate that 30 percent of all patients getting placebo treatment today improve.

The effect is profound in disorders like Parkinson's, where patients have good days and bad, and in those diseases where pain is common. And it is likely to be especially powerful in an intervention as dramatic as surgery, said Dan Moerman, a medical anthropologist at the University of Michigan at Dearborn. "There is probably more need for placebo tests in surgery," he said, "than in other areas of medicine."

In 1962, the Food and Drug Administration decreed that placebo-controlled clinical trials, those in which half the patients are treated and half get dummy pills, were the gold standard for new drug approvals. Traditionally, the FDA has taken a hands-off approach to surgical innovations. But that is changing, now that biotech firms are using surgery to implant genetically engineered cells that the agency classifies as drugs. When Genzyme Corp. of Cambridge, Mass., proposed injecting pig cells into the brains of Parkinson's patients, the agency insisted on a placebo design.

The patients in all the studies know they stand a chance of not being treated. But keeping patients in the dark can pose problems beyond performing fake operations, as Genzyme found. The patients getting the pig cells will receive anti-rejection drugs and antibiotics, standard fare for transplant patients. The placebo patients will get dummy anti-rejection pills. But making fake antibiotics that look, taste and smell like the real thing was impossible, said Dr. J. Stephen Fink, a neurologist at Genzyme, and so the sham surgery patients will get real antibiotics.

That prompted the ethics board at Columbia Presbyterian Center in New York City, which helped run the fetal cell experiment reported last week, to turn down Genzyme's project. The research is now proceeding elsewhere. "We really struggled with the decision," Fink said, "because it isn't an ideal thing to do."

The common wisdom in ethics circles is that in routine health care, intentionally deceiving patients is wrong. But the debate over sham surgery raises an obvious question: If phony operations can help people, why not just do them? "That," said Dr. Wray, the Texas knee researcher, "is an important point. What to do with it, medicine is going to have to decide."