The Olympic Games celebrate majesty of the human body as a perfectly tuned machine, and the spirit that pushes that machine to its limits. Olympic athletes stretch the very fabric of human performance, smashing world records with their grit, heart and sweat.

And performance-enhancing drugs.

Who can blame them? The absolute limits of non-enhanced human athletic performance may well be set in stone. Bones don't get stronger from one generation to the next. The amount of power that muscles can generate is limited, as is the amount of oxygen that can be ferried by blood. What remains constant is the public clamor for new world records.

Performance-enhancing drugs are banned from Olympic competition, but it is a ban that has been honored in the breach. From the brute steroids the East Germans reportedly used on their Olympians during the Cold War to today's man-made versions of natural human proteins, drugs have been as much a staple of the Games as gold, silver and bronze.

Throw in the fact that some of the new drugs are used safely for clinical purposes and are nearly impossible to detect, and widespread use seems inevitable. That's the reality of competitive 21st-century sport.

Charles Yesalis, an epidemiology professor at Pennsylvania State University who has written extensively on the use of performance-enhancing drugs in sport over the past 23 years, believes a "large percentage" of record-holders probably doped their way to the finish line. "A lot of experts, at least in private, feel that way," he says.

One often abused performance-enhancing drug is erythropoietin, a protein that was the biotech industry's first blockbuster and is still its biggest drug.* Erythropoietin--also known as EPO--generated more than $5 billion in 2001 sales for inventor Amgen (nasdaq: AMGN - news - people) and licensee Johnson & Johnson (nyse: JNJ - news - people).

For many, EPO dramatically improves quality of life. The protein spurs the body to produce more oxygen-carrying red blood cells, which in turn allows the blood to carry more oxygen. Doctors prescribe it for the anemia that occurs with kidney failure and chemotherapy. But for an athlete, the same protein can increase endurance by allowing the blood to ferry more oxygen to hungry muscles. This is risky: Dopers also might make their blood so thick, they induce heart attack from the stress of pumping it.

"There's definitely a performance-enhancing effect if you use things that improve oxygen transport to the tissue," says Larry Bowers, an expert on athletic drug testing and senior managing director of the U.S. Anti-Doping Agency. He says anonymous surveys of athletes indicate that only a tenth of them use performance-enhancing drugs. But he acknowledges that doped athletes may win most of the time. Yesalis maintains that drug testing, as practiced at past games, has been a "farce."

"Just because of my own value system, I have never seriously entertained legalizing drugs," says Yesalis. "But the stench of the hypocrisy is starting to outweigh my hesitation to just throw up my hands and say, 'Let everybody do whatever they want.'"

For years, EPO has been difficult to detect with standard urine and blood tests. Newer tests that may pick up EPO use can not detect Aranesp, Amgen's newer, longer-lasting version of the protein.

In the near future, drug testing may be of little use. Gene therapy, a set of medical technologies that plant new genes in a person's cells in order to produce missing proteins, might be used both to save lives and to ramp up athletic performance. And if the past is any guide, it won't be long before the technology moves from the laboratory to the training field.

Malcolm Brenner, a professor at the Baylor College of Medicine and the current head of the American Society of Gene Therapy, says that such gene therapy is already being done. A researcher at Baylor is working on a therapy that would allow cancer patients to produce extra human growth hormone (HGH), lessening their symptoms.

A ring of DNA containing a gene that starts the body producing extra HGH is injected into the patient's muscle. These cells start to produce the hormone, boosting levels of it in the body more smoothly than occurs with injection. The work looked promising in animals, and the researchers wanted to move on to human trials.

Human gene therapy trials are tightly controlled. The Recombinant DNA Advisory Committee, a division of the National Institutes of Health that approves all gene therapy experiments, has yet to make a decision on whether this technique should move into the clinic. But one concern they brought up is that athletes, some of whom already inject HGH, might use this gene therapy instead.

It does not make sense to not treat sick people in order to prevent healthy athletes from cheating. Instead, we should focus on preventing performance-enhancing drugs from making the athletes sick.

One step in the right direction is to focus on the dangerous side effects, not the drugs themselves. Bowers says that this year, endurance athletes like speed skaters and cross-country skiers are being tested to see if their blood is too thick with red blood cells. That can be a side effect of abusing EPO. But the athletes would not be blamed; instead, their health would be protected.