What exactly is the stuff Bonds allegedly took?

If Barry Bonds took the drugs prosecutors claim he did, the home run king wasn't strolling through a steroids warehouse and blindly pulling stuff off the shelves. He, or his consultants, knew precisely what they were doing.

Methenelone. Nandrolone. Tetrahydrogestrinone. Clomiphene. Exogenous testosterone.

The average sports fans might need a scorecard – or, in this case, a chemistry book – to identify the drugs for which the government says Bonds tested positive. But Anthony Roberts, a steroid expert, recognizes the performance-enhancing substances as cocktail ingredients for any world-class athlete.

"It's a pretty well thought-out cycle," said Roberts, author of "Anabolic Steroids: Ultimate Research Guide." "You're going to gain strength, muscle, no fat, no water and your injuries are going to just disappear."

During the government's investigation, an undercover cop shadowing Bonds bought a membership to Gold's Gym. It's where Bonds spent several hours a week lifting weights, proof that his workout regimen included more than popping pills.

But the government seized ledgers that suggest Bonds had chemical help. Although Judge Susan Illston on Thursday indicated she might throw out the positive drug tests as evidence, her decision has more to do with legality than reality.

Bonds never denied using steroids, only that he did so unknowingly. And he hasn't denied those positive drugs tests are his, or what they show about his possible drug use.

Three positive drug tests in 2000 and 2001 linked to Bonds showed the presence of methenelone, better known as Primobolan, and nandrolone, better known as Deca-Durabolin. Bonds hit a then-career-high 49 home runs in 2000 and set the single-season home run record of 73 in 2001 at age 37.

Deca-Durabolin is the steroid that Jason Giambi, the former Yankees slugger now with the A's, told the BALCO grand jury he was taking. Mark McGwire's brother Jay recently claimed he injected McGwire with the same drug.

The steroid apparently was a favorite of hundreds of ballplayers supplied by Kirk Radomski, the former clubhouse attendant for the New York Mets and a central figure in Major League Baseball's investigation into the use of steroids.

"At first everybody in baseball was using Deca-Durabolin," Radomski wrote in his recently released book, "Bases Loaded." "… Deca helped relieve soreness in shoulders and joints; it's particularly good for reducing the impact of groin injuries. For pitchers, Deca is particularly great for increasing strength and reducing some of the soreness in the elbow joint. It builds muscle but not so much that it begins to effect flexibility.''

Primobolan, a mild steroid, was less popular among players because travel during the season made it difficult to sustain the 12-week cycle needed to realize the full benefits, Radomski wrote. Bonds allegedly tested positive for Primobolan in the offseason.

But for Bonds or any other baseball player, the use of Deca-Durabolin and Primobolan became problematic in 2003. That's the year baseball started testing for steroids.

Deca-Durabolin stays in the system for up to 18 months. Bonds or his trainer, Greg Anderson, allegedly kept him one step ahead of testing, according to prosecutors.

By 2003, Bonds was working with BALCO, which distributed Tetrahydrogestrinone (THG), better known as "the Clear.'' At the time it was undetectable.

The substance was allegedly found in Bonds' urine sample only after Dr. Donald Catlin, a prominent anti-doping figure, developed a test to identify THG and in 2004 re-tested Bonds' urine sample submitted during baseball's survey testing in 2003.

The Clear was being taken in conjunction with Clomiphene, a mild anti-estrogen steroid, and exogenous testosterone, testosterone produced outside of the body, according to a supposedly anonymous Major League Baseball drug test in 2003 the government says belongs to Bonds.

Makes sense, according to Roberts.

"As an athlete, you're getting the benefits of the THG, the strength," he said. "And instead of feeling shutdown, suffering from low testosterone, he's going to replace that testosterone so he's not going to feel rundown."

While Bonds has denied he knowingly took steroids – which is the crux of the case in which he faces 10 counts of perjury and one count of obstruction of justice – he had access to a trainer, Greg Anderson, who consulted BALCO mastermind Victor Conte. Records seized in a 2003 raid on BALCO suggest athletes were using sophisticated doping regimens.

Proper use of steroids is something other baseball players failed to grasp, according to Radomski.

In his book, Radomski recounts a discussion he allegedly had with Lenny Dykstra when the former All-Star for the Philadelphia Phillies showed up for the 2000 season. Dykstra had put on about 35 pounds. Radomski wrote that he warned Dykstra would shrink in the heat of the summer and sap the newly gained strength, and that's precisely what happened, according to the book.

"A lot of people believe all steroids are the same," wrote Radomski, who began distributing to players and advising them in the late 1980s. "They're not, because each steroid works differently in your body and has a range of side effects that can mess you up if they aren't being used correctly."

Methenelone. Nandrolone. Tetrahydrogestrinone. Clomiphene. Exogenous testosterone.

The drugs in the government's exhibits, and evidence that purportedly shows how Bonds ingested them in cocktail form, underscores a sophisticated understanding of the performance-enhancing substances.

This was no Dykstra. Whatever Bonds allegedly used helped transform him from a sturdy hitter with considerable power into baseball's home run king.

What do the drugs do?

Anthony Roberts, a steroid expert, explains the physiological effect of the steroids and other substances for which the government said Barry Bonds tested positive.

Primobolan (methenelone): This is a quality lean mass gainer. No water, no fat, just strength and muscle. It's the most expensive steroid on the market, and the most counterfeited as a result.

Deca-Durabolin (nandrolone): This is highly prized for its ability to soothe injuries and repair bone and connective tissue. It's got a well-deserved reputation as a lean-mass gainer. Athletes who are not drug tested will look to Deca for their cycles. It's also a nice stack with Primobolan, as they have very disparate effects.

THG: It's highly anabolic, and causes great strength gains without much weight gain. It also causes an extreme shutdown of the body's natural testosterone, resulting in potential sexual dysfunction. Most users on similar drugs (i.e. Trenbolone) find it necessary to supplement their cycle with testosterone to avoid sexual dysfunction and other side effects.

Clomid: This is a mild anti-estrogen and testosterone stimulator. It's likely that it was used on this particular cycle to make postcycle recovery of natural hormones easier.

Testosterone: This is a good strength and mass builder. It is almost always used with drugs like THG because it replaces your own testosterone (which is greatly inhibited by THG) with a synthetic version. As you wouldn't have had any testosterone at all, this replaces what's lost, and your body functions as normal.