or three decades, the International Olympic Committee has been engaged in a game of chemical cat-and-mouse. Athletes use drugs to enhance their performances, scientists devise tests to identify those drugs, then the athletes move on to more sophisticated doping techniques.

Now, the rules of the game may be changing, leaving the Olympic committee even further behind.

Concerned that athletes would soon employ genetic engineering in attempting to run faster, to jump higher and to throw farther, the I.O.C. and the affiliated World Anti-Doping Agency are about to convene inaugural meetings on the subject. "For once we want to be ahead, not behind," Dr. Patrick Schamasch of France, the I.O.C.'s medical director, said.

Genes serve as a script that directs the body to make proteins. It seems fantastic today to think that injecting a gene could result in more fast-twitch muscle fibers, enabling a sprinter to run 100 meters in six seconds instead of just under 10. Or injecting a gene that could increase oxygen-carrying capacity so that a marathoner could run 26.2 miles in one and a half hours instead of just over two. Some scientists and Olympic committee officials believe genetic engineering in sports is a decade away. Some believe it may appear in two years. Still others believe crude forms might already be in use, at great health risk to athletes.

"I think certain methods could have already started," said Johann Olav Koss, the 1994 Olympic speed skating champion from Norway who is a member of the I.O.C. and a doctor.

Medical applications of gene therapy — efforts to cure or prevent disease — are at a very rudimentary stage, with only one form of gene therapy having been shown conclusively to work. Little is understood about the implications of introducing genes into a human body, so any use aimed at improving athletic performance would now be considered dangerous and unethical.

But the human genome has been mapped out and the technology, however immature, is evolving rapidly. Athletes, who are often eager for an edge in competition, are not very likely to wait for science to perfect gene therapy. Inherently, athletes are risk takers. And there is enormous financial pressure and reward to win, to produce records and to keep up with other athletes who are succeeding through illicit means.

Genetic engineering in sport will foster not only a greater potential health risk for athletes than does conventional doping, but also a greater potential for performance enhancement, said Dr. Jacques Rogge, a Belgian surgeon who is an I.O.C. delegate and vice chairman of its medical commission. Instead of repeatedly ingesting pills or taking injections, an athlete may be able, with a single insertion of genetic material, to sustain bulked-up muscle mass or heightened oxygen-carrying capacity for months or even years. Such genetic manipulation would be extremely difficult, if not virtually impossible, to detect using current methods, scientists said.

At the coming meetings of the Olympic committee and the anti-doping agency, officials will discuss the potential benefits and risks of genetic engineering and the potential detection methods, and they will face a number of ethical questions. Should genetic manipulation be banned entirely in sport? Should it be allowed for athletes healing from injury or recovering from disease? If the technology can be made safe, do healthy athletes have the right to engineer themselves like race cars to push the boundaries of achievement? Will two classes of competition be needed?

"What if you're born with something having been done to you?" Maurice Greene of Los Angeles, the Olympic champion at 100 meters, said. He wondered, would manipulation of an egg or an embryo be considered cheating? "You didn't have anything to do with it," he said.

The Olympic committee scheduled a meeting for June 6 on genetic engineering only after the anti-doping agency announced plans for its own gathering in September, an apparent political gesture to appear out front on the issue, said Dr. Arne Ljunqvist of Sweden, who is an I.O.C. delegate and chairman of the anti-doping agency's medical, health and research committee.

The second meeting is considered the more significant of the two; the agency hopes to gather three dozen athletes, sports scientists, genetics experts, ethicists and policy officials from the Food and Drug Administration and the National Institutes of Health in Cold Spring Harbor, N.Y.

"For the first time, a substantial group of people involved in sports administration, sports science and genetic science will sit around the same table and discuss a common potential problem," Dr. Ljunqvist said.

The concerns range from the pragmatic to the philosophical. Do the Olympic committee and other sports organizations have the willpower or financial resources to combat the use of genetic engineering? The total cost of conventional drug tests are already about $1,000 each.

Ultimately, at the heart of the issue will be a profound question: what is a human athlete?

"What are the endpoints of manipulation?" said Dr. Theodore Friedmann, director of the gene therapy program at the University of California at San Diego and a member of the anti-doping agency's health and research committee. "Is the hope to incrementally sneak up on the one-and-a-half-minute mile? Or six seconds for 100 meters? Is the question, How fully can we engineer the human body to do physically impossible things? If it is, what do you have at the end of that? Something that looks like a human, but is so engineered, so tuned, that it's no longer going to do what the body is designed to do."

Anything for an Edge?

Athletes, scientists and sports administrators agree that someone will attempt genetic engineering, if they have not already. Concern over health and safety issues has not been a strong deterrent to the epidemic use of conventional performance-enhancing drugs.

In a 1995 survey, nearly 200 aspiring American Olympians were asked if they would take a banned substance that would guarantee victory in every competition for five years and would then cause death; more than half answered yes.

A recent seminar on teenage steroid use, held in New York City, revealed these desperate efforts to boost athletic performance: A female basketball player asked a doctor to break her arms and reset them in a way that might make them longer; pediatricians were being pressured by parents to give their children human growth hormone to make them taller and perhaps more athletic; doctors were being asked by the parents of football players to provide steroids so their sons might gain college scholarships.

A molecular scientist, speaking on condition of anonymity, said in an interview that a foreign exchange student staying with the scientist's family was approached at a swimming pool by a stranger and was told, "You are absolutely beautiful; I'll give you $35,000 for one of your eggs." The student accepted the offer. It is not inconceivable that some parent looking to create an elite athlete would offer far more money for such an arrangement with, say, Marion Jones, the world's fastest woman.

"In theory, you could do in vitro fertilization, stick in a gene for x, y or z and you've built a kid," the scientist said. "It's been done in mice. But I'd consider that brave new world stuff. It's not happening with humans."

Other techniques now being tested on lab animals seem much less futuristic. For instance, the gene that codes for the hormone erythropoietin, or EPO, has been identified. Produced by the kidneys, EPO regulates the production of red blood cells. A synthetic version can serve as a wonder drug for patients suffering from anemia, AIDS or cancer. Because it enhances oxygen-carrying capacity, EPO is believed to be in widespread use in such endurance sports as cycling and distance running.

Conventional illicit doping measures require athletes to be injected at regular intervals with EPO to maintain the endurance benefit. The insertion of a gene, however, could theoretically turn the body into an EPO factory. Last year a study by Dr. Steven M. Rudich, a transplant surgeon then at the University of California at Davis, indicated that a single injection of the EPO gene into the leg muscles of monkeys produced significantly elevated red blood cell levels for 20 to 30 weeks.

"An athlete would be out of his mind to want to use this," Dr. Rudich, who is now at the University of Michigan, said. Ruefully, he said about genetic engineering in sports, "I bet it exists."

Muscular Mice

Genetic material can be delivered to the body by several methods. Dr. Rudich took a weakened virus, inserted a snippet of EPO gene, then injected it into the monkeys' thigh muscles. Each gene consists of DNA, the ladder-like structure that serves as a genetic carpenter, instructing the body what to construct. In this case, the DNA signaled the muscles to produce EPO, which stimulated the production of red blood cells.

Other hormones and proteins that can be used in gene therapy for performance enhancement are human growth hormone and a protein called insulin-like growth factor-1, or IGF-1. Growth hormone can be used to treat dwarfism in children and to prevent muscle loss in the aging process. IGF-1 is critical to the repairing of muscle tissue. Both substances are believed to be used illicitly now by athletes using conventional methods to increase muscle size and strength.

Ten years ago, Dr. Helen Blau of Stanford demonstrated that a gene could be introduced into a mouse to stimulate production of normal levels of human growth hormone in the bloodstream for as long as three months, compared with 10 minutes if the drug were taken directly. Recently, she and others showed that oral antibiotics could be used as a switch to turn the gene on and off.

"In theory, it is possible that an athlete could be genetically engineered to have a gene so you could increase muscle strength, train with it and shut it off when you want to, which would make drug testing more difficult," said Dr. Blau, chairwoman of the department of molecular pharmacology at Stanford Medical School. "Whether it's happened, I have no idea. In theory, it's possible. It's something to keep an eye on. It could be a future concern for the Olympics."

A 1998 study by scientists at the University of Pennsylvania and Harvard involving IGF-1 used gene therapy in mice to halt the depletion of muscle and strength that comes with old age. Older mice increased their muscle strength by as much as 27 percent in the experiment, which suggested possibilities for athletes as well as for preserving muscle strength in elderly people and increasing muscle power in those who suffer from muscular dystrophy.

"We called them Schwarzenegger mice," said Dr. Nadia Rosenthal, an associate professor at Harvard Medical School and a co-author of the study. It has since been demonstrated that mice enhanced with the IGF- 1 gene continue to gain size and strength when exercising on a wheel without any apparent adverse health effects, she said.

"I'd be totally surprised if it was not going on in sports," Dr. Rosenthal said, speaking generally of crude attempts at genetic engineering. "Those with terminal cancer and AIDS want to know, `What will keep me alive?' Athletes want to know, `What will make me win?' "

Hidden Dangers

The danger in attempting genetic engineering now for athletics, Dr. Rosenthal and other researchers cautioned, is that experiments with mice and monkeys might not work the same way in humans and might lead to negative side effects.

If a gene for producing EPO cannot be shut off properly, the blood will begin to thicken with excessive red blood cells and that could cause strokes and heart attacks.

If the gene for human growth hormone is not regulated, muscles might grow until they outstripped the blood supply or overwhelmed tendons and ligaments. Misuse could also lead to heart and thyroid disease and cause the size of someone's head, jaw, hands and feet to increase dramatically.

The entire process of genetic engineering remains imprecise. Dr. Thomas Murray, president of the Hastings Center, a biomedical ethics research institute in Garrison, N.Y., likened it to firing at the bull's-eye of a target with a spray of shotgun pellets. It is not known exactly where the virus and DNA go when injected, how they get where they are going or what the body's immune response will be.

An attempt to strengthen the shoulder muscles of a javelin thrower, for instance, might lead inadvertently to an enlargement of the heart muscle. Or worse. A teenager died in 1999 during a therapeutic study at the University of Pennsylvania, apparently in reaction to the virus carrying genes intended to treat a metabolic disorder.

"We don't know the technology well enough even to be sure what's happening in a therapeutic setting," Dr. Friedmann of California-San Diego said. "We certainly don't know the technology well enough to know how safe a gene is going to be to an athlete."

Before athletes are fitted with designer genes, the next advance may be to create more synthetic versions of drugs like EPO and growth hormone that mimic the effects of genetic engineering, scientists said. But genetic manipulation of the human body for sport is sure to come. The question is, to what extent?

Michael Johnson, the Olympic sprinting champion, said he thought the health risks would scare off many athletes. Werner Franke, a German molecular biologist who helped bring to light the systematic doping of athletes by East Germany, said he was not particularly worried about genetic engineering because chemical footprints left by the inserted virus and DNA would facilitate detection.

"I think it will be mostly science fiction," Mr. Franke said. He accused the I.O.C. of "purposely barking up the wrong tree" in an attempt to camouflage its lack of commitment to catching athletes who cheat by conventional methods.

Many scientists, however, disagree with Mr. Franke's assessment of the potential ease of detecting altered genes. With available technology, they say, scientists would have to know exactly where the gene was inserted in order to identify it, which would most likely require muscle biopsies.

"No athlete in his right mind is going to allow himself to be probed here and there for evidence of a virus," Dr. Friedmann said.

Eventually, some noninvasive detection methods might be developed, like chemical markers or a chip that could be encoded with the sequence of a specifically altered gene. But some researchers believe that only a change in cultural attitudes will curb genetic engineering, just as a cultural shift has led to an intolerance for smoking.

"We have to change the fundamental mind-set about doping," Dr. Don Catlin, who operates the Olympic drug-testing lab at U.C.L.A., said.

There appears to be little fear that human cloning will have a significant effect in sport. If say, Michael Johnson were cloned, the result would almost certainly not be the same world record-setter as the original, researchers say, because environmental, nutritional and motivational factors also play significant roles in developing athletes.

"If I'm the clone of Michael Johnson, I've got to bend myself into all sorts of shapes to run, because genetically that's what I'm destined to be," Dr. Friedmann said. "I run and run and run, and I can't ever get anywhere. Then what am I? I'm a Michael Johnson who can't run. That's a nobody. That must be a crushing experience to learn you're not what you're genetically destined to be."

Moral and Athletic Limits

Cloning aside, many athletes and sports officials say they would abhor genetic engineering in sport. "It is supposed to be a test of human capability, not a chemical war or a genetic war," Brandi Chastain of the American women's soccer team said.

If genetic engineering is used, "then sport is dead," said Dr. Bengt Saltin, director of the Center for Muscular Research at Copenhagen University in Denmark.

Yet, American society tolerates other types of enhancement, from the caffeine stimulation of coffee to breast enlargement to erectile function. And although there has been an outcry about genetically engineered corn, there was mass celebration when Mark McGwire broke the major league home run record in 1998 using androstenedione, a steroid precursor that is banned by the Olympics and many professional sports.

"Nobody cared about what McGwire was using," said Jon Drummond, a member of the victorious American 4x100-meter relay team at the Sydney Olympics. "They just wanted to see him break the record."

If genetic engineering can be made safe, with fewer side effects even than conventional methods of doping, it may grow increasingly difficult to find supportable arguments against using gene alteration to achieve excellence in sport, Dr. Friedmann said.

"Our society has already decided partly that maybe there isn't a lot wrong with it, and that we can build ourselves, change ourselves, as much as we'd like, consistent with safety and medical ethics," he said. "If a weight lifter makes massive muscles and with a flinch of the finger can lift a few hundred pounds, what's wrong with that ethically? I'm not sure you'll get good answers to that."

Not all athletes will have equal access to genetic engineering, but not all of them have equal access today to the same nutrition and training facilities. Not every distance runner, for instance, can train at altitude. Should sea-level athletes be allowed to take EPO to match the oxygen-carrying benefits for those who live at altitude?

The most effective argument against genetic enhancement may be that it will coerce others to alter their fundamental makeup, perhaps at great risk, if they want to compete.

"The argument in favor of allowing people to do this is based on our American tradition of giving individuals a huge amount of autonomy over their own bodies," said Dr. Eric Juengst, an ethicist at Case Western Reserve University in Cleveland. "The limits on that kind of freedom are interpersonal. Once your actions cross the line of affecting just yourself and begin to affect other people, we have license to step in."

That right to set moral limits, however, will inevitably clash with a desire to break athletic limits. Anyone who could run 100 meters in six seconds "has no place in sports," said Mr. Greene, the world record- holder at 9.79 seconds. But, he added, "If anyone can run the 100 in six seconds, I'd like to see it."

Category: 32. Genome Project and Genomics, 50. Gene Therapy