As drug testing gets more sophisticated, so does cheating. In fact, scientists fear they may one day have to test not only blood and urine, but also genes: As genetic research and manipulation become more commonplace, athletes may find ways to reprogram their genetic codes to become stronger and faster.

For now, cheaters have to settle for less futuristic methods that simply keep them one step ahead of the latest drug-testing technology.

"The sophisticated doper ... can get away with it," said Donald Catlin, head of the IOC Olympic drug-testing lab at UCLA. "We have to concede that."

So how does the doper do it?

Low-tech

He can substitute someone else's urine for his own.

This is not easy. Because drug-testing officials watch athletes give samples, an athlete can't just carry a vial of urine in his pocket. He would have to fill his bladder with another person's urine using a painful catheter, risking serious infection, or hide a pouch of urine in another body cavity.

He can store some of his own blood and reinfuse it before

competition.

This original form of blood doping is fraught with risk of infection and other complications. Some athletes who tried it became too ill to compete. The injection of erythropoeitin (EPO) has largely replaced this practice.

High-tech

He can take a masking agent to dilute or cover up the drug.

However, masking agents and diuretics are banned and some are detectable in a urine test.

He can boost his testosterone levels without going over the maximum allowable standard.

The average testosterone/epitestosterone ratio is 1:1. The IOC's limit is 6:1. An athlete whose normal ratio is 1:1 can quintuple his testosterone level without exceeding the limit.

He can use a drug that is undetectable, such as human growth hormone (hGH) or EPO.

Tests are in the works, but are not yet perfected.

Super high-tech

He can use a mimetic, which is a drug that acts like a banned drug but isn't yet detectable.

As scientists perfect tests for synthetic EPO and hGH, other scientists are developing a drug that acts like EPO and a hormone that releases more of the body's natural supply of hGH.

How to Fail a Drug Test Without Even Trying

You don't have to take steroids to fail a drug test. Some of the stimulants prohibited by the IOC can be found in over-the-counter medicines. In fact, most products labeled `decongestant' contain banned substances.

Drug name

Found in products such as

Ephedrine

Bronkaid, herbal teas containing Ma Huang

Pseudoephedrine

Actifed, Co-Tylenol, Sudafed, Drixoral

Desoxyephedrine

Vicks Inhaler

Phenylpropanolamine

Allerest, Alka-Seltzer Plus, Contac, Sine-Off, Triaminic

In addition to over-the-counter medications, some common prescription drugs are also prohibited.

Drug name

Found in prescriptions

Amphetamine

Benzadrine, Obetrol

Ephedrine

Bronkotabs, Primatene

Bromantan

Bromantan

Methylphenidate HCL

Ritalin

Salbutamol*

Albuterol, Bentolin, Proventil

Terbutaline*

Brethaire

*Allowed in aerosol or inhalant form with written notification

Because so many prohibited substances can be found in so many commonly prescribed drugs, athletes carry a wallet-sized card distributed by the USOC that alerts physicians and hospital personnel to the types of drugs they shouldn't be given.