"OK," the doctor said when we settled into his examination room. "What do you want to be?"

I looked confused, so he explained.

"You want to be bigger? Leaner? Faster longer or faster shorter? More overall endurance? You want to see better?"

"See better?"

"Human growth hormone does that for some people. It improves the muscles in the eyes." He tried again: "So, what do you want?"

This was quite a concept. Freud wrote that anatomy is destiny, and here was a doctor giving me a chance, in my late forties, to alter my body in the most fundamental way. It was strange, but also strangely alluring.

It had taken me a while to arrive at this moment. I was sitting in the San Fernando Valley offices of a physician whose identity I've agreed to conceal—let's just call him Dr. Jones. For reasons I'll explain shortly, my goal was to experience firsthand some of the banned performance-enhancing drugs that are often abused in the endurance sports I participate in, like cycling and cross-country skiing. The menu I had in mind included human growth hormone (HGH), testosterone, and some variety of anabolic steroid, all of which are used to increase strength and shorten an athlete's recovery time by repairing muscle cells faster. Also high on my list was that powerful stuff called erythropoietin, better known as EPO, a hormone that boosts oxygen levels in the blood by prompting the bone marrow to produce more red blood cells. EPO is known to have amazing endurance-boosting effects; not surprisingly, it's been a scourge for years in professional biking and skiing. In 1998, to cite one famous example, the Tour de France nearly came to a halt when a leading team, Festina, was caught using EPO, HGH, steroids, and testosterone. The entire squad was disqualified, and dozens of riders either staged protests or withdrew in reaction to the drug tests and police raids that followed.

All of these are prescription drugs, and they all have legitimate medical applications. (HGH, for instance, is used to treat Prader-Willi syndrome, a rare disease that stunts the growth of children.) But you and I are not supposed to have them without a doctor's supervision, and they're absolutely forbidden in most higher realms of sports. There are exceptions—Major League Baseball doesn't drug-test at all—but if you were caught using these substances in, say, the Olympics, the Tour, the NFL, or any NCAA event, you would face disqualification and suspensions, though the penalties and the testing processes vary wildly. This is one of the key problems that the World Anti-Doping Agency (WADA), an independent drug-policy group headquartered in Montreal, is attempting to address—with the goal of standardizing everything from a list of banned drugs to the testing-and-appeals process. WADA's hope is that these rules and procedures will be adopted by sports federations around the globe.