INDIANAPOLIS, AUG. 19 -- Rob Stull is a 26-year-old undergraduate with one of those fraternity row haircuts, a pair of Levi's 501 jeans, and a button-down shirt. Most of his friends have already gone to Wall Street, where under normal circumstances he probably would be. Instead, he is here at the Pan American Games, winning medals at something called, what, the modern penthouse?

Modern pentathlon. It's that event that seems to go on forever and generally involves an Army officer riding a horse, shooting a rifle, swordfighting, jogging and swimming. It's an obscure event practiced mainly by those who someday plan to join the Palace Guard or go to the Olympics. The latter is the aim of Stull, a product of Clarksburg, Md., and Damascus High School. He won a Pan Am gold medal last week inthe pentathlon competition, and tonight earned a silver in the epee team fencing competition.

The Pan Am Games are part of Stull's dress rehearsal for the 1988 Olympics in Seoul. The Olympics are the primary reason why Stull is on what he calls "the eight-year college plan," in pursuit of the gold medal that eluded him in 1984 in Los Angeles. Although he was part of the team that won the silver, it was a bittersweet experience, marked by accusations of cheating during the trials and his status as just the fourth man.

In a drug test last year, he tested positive for what he says was inadvertent use of a cold remedy. He was fined $3,000 and now is tested everywhere he goes. America's best hope in the pentathlon in 1988, Stull also has unintentionally become one of the sport's more controversial figures. A medal would greatly redeem the last four years.

"The problems have kept me in it," Stull said. "Now, I'm not in it for the sweats. I'm in it for the medal."

Stull is an unlikely source of controversy. We're talking yuppie, and proud of it -- one of those amicably ambitious guys stamped out by universities like Texas. He transferred there for its pentathlon program from North Carolina State, where he was a swimmer. His parents John and Dorothy ("Like the Wizard of Oz," he said) live in Gaithersburg, where John is in nuclear power research and development for the Bechtel Corp.

Stull has a quick, wry sense of humor that has enabled him to keep his perspective in view of his misfortunes. If he weren't still pursuing gold medals, Stull says, "I'd be riding the Dow Jones for all it's worth."

He probably could have retired after 1984 and done just that, somewhat content with a silver medal. But the memories of headlines like "Stull Cheats" left a bad taste in his mouth, as did the fact that he was not a competitive member of the team. At the trials in May 1984, two men who did not make the Olympic team accused Stull and some friends of his of rigging matches to make sure Stull earned a place on the squad.

According to Bob Mienan and Mike Burley, two renowned pentathletes who did not make the team, Stull's friends were throwing fencing matches in his favor to give him the points he needed. He was cleared in proceedings held by the U.S. Pentathlon Amateur Federation in San Antonio, at which fraternity friends carried signs that read, "SOS: Save Our Stull." But the damage was done.

Stull filed a defamation of character suit against the heads of the federation, which was settled out of court two weeks ago. He had to fight for his original place on the 1984 Olympic team, which did not want him to compete because of the scandal. As fourth man, his job was to scout the equestrian courses, work with horses and equipment and generally do anything he could to help. It was some consolation that the U.S. took a silver, edging France by three points.

"A lot of people said, how could I compete under those circumstances," Stull said. "I said, 'How could I not?' "

Accusations of cheating are not at all unusual in the pentathlon, or in fencing. Over the years, shooters have been revealed to have taken sedatives in order to steady themselves, and fencers are notorious for using glue or nail polish on the ends of their blades, hoping to set off one of the electrical charges that signify a point.

Stull is a passionate defender and energetic publicist of his event, so he is clearly uncomfortable with the unwanted attention he has brought to it.

If Stull's misfortunes seem too frequent to be bad luck or coincidence, consider his past. He was a kicker on his high school team and had potential to kick in college until he was speared by an opponent, ruptured his pancreas and almost died. When he told his father he wanted to learn how to fence, John Stull refused to buy him the equipment because he was afraid his son would get an eye poked out.

He settled for swimming and running, and finally took up fencing in college. He learned to shoot and ride on his parents' farm as a child, and a gym coach at North Carolina State suggested pentathlon. Stull leaped at it.

"I'm a competitor," Stull said. "Unfortunately, I don't have Herchel Walker's body, so I've had to make do."

Despite his gold medals here, Stull will be something of a long shot at the '88 Olympics in a sport that has been dominated by Eastern Bloc countries. But he ranks among the top six in the world, and is well versed in competing against Eastern Bloc opponents. First, of course, he has to make the team without further incident.

"The best thing that could happen is if I make the team, go to Seoul, and win," he said. "That would be a good ending to an unhappy four-year story."