Mark Talbott's sport is the epitome of the Ivy League, of private clubs, of money so old it breeds. His was one of the founding families of Dayton, Ohio.

"Our cobblestone driveway was the city's old Main Street," Talbott said.

But while he is ranked as the very best squash player in North America, Talbott earned "just a little more than $20,000 last year" and travels from tournament to tournament in a makeshift van.

"I guess I really don't have a place of my own to call home," he said. "My van is a kind of A-framed thing and the walls were taken from an old squash court my brother used to play at. It's all white in there."

Talbott's world is indeed pristine but for the little green ball smacking off the walls. The 18.5-by-32-foot four-walled court most resembles the "rubber rooms" of popular fiction.

Talbott's grandfather was a wealthy stock investor and businessman--"I don't know all the businesses he was into." The Talbotts lived in the grandfather's huge Dayton mansion until seven years ago, when they sold the house and moved to Atlanta. The family played squash in a basement court and Talbott played best.

"The whole thing was covered with chicken wire," he said of the patriarchal court. "The only way to get in there was by lowering yourself in by a ladder. I sort of grew up in there, so it doesn't seem weird at all for me to be playing professional squash."

Talbott is lithe, long-haired and 22. He has a crooked smile that suggests prep school, a life of professional, peripatetic leisure. But his aggressive, leonine skill on the court is fairly ferocious. He has won 13 of his 14 tournaments, losing only once to sixth-ranked Ned Edwards. Last night, he beat Edwards, 15-13, 12-15, 15-9, 13-15, 15-11, in an exhibition at the Capital Hill Squash Club.

Among other strategies, Talbott makes great and surprising use of the "double boast," a tricky shot that bounces off both side walls before hitting the front wall and "dying" before an opponent can reach it. Such a shot requires the power of Rod Laver and the geometry of Euclid.

The North American top ranking has been dominated in the last decade by Sharif Khan, a 36-year-old Pakistani. Five other members of the Khan family are ranked in the top 35 by the World Professional Squash Association. In an effort to stave off middle age and a new generation of players, Khan has transformed his game of late, turning from power to finesse. He is now ranked third and Michael Desaulniers, 25, a Harvard-educated commodities trader, is ranked second.

Talbott ascended to the top rung with a victory in the Chivas Regal Open held in New York last November at the Uptown Racquet Club. The tournament is the biggest of the 27 that make up the sport's October-to-May season.

"That was big, but the tournament that really got me going was three years ago . . . here in Washington," said Talbott. "Not many people had heard of me and I won. I beat four of the top five players: Desaulniers, Khan, (Clive) Caldwell and (Stuart) Goldstein."

Talbott joined the professional squash tour earlier than most of its select players. After graduating from Mercersburg Academy, a prep school in Pennsylvania, he entered Trinity College. He lasted only one semester.

"I liked the friends I made at Trinity but I wasn't much on the studying," he said, resting before the exhibition. "I feel natural here."

All the top players are hoping that the popularity of squash will increase; if that happens it may mean bigger crowds, bigger purses, more lucrative endorsement contracts.

Squash players are generally born to money--if not to the manor, then at least to the upper-middle class. And though Talbott and others are trying to rip some of the ivy off the court walls, the sport's origins bespeak a certain breeding.

In the 1880s, London's Fleet Prison housed many a high-born debtor. To pass the time, the prisoners paddled a ball around the institution's halls. The game spread to other prisons and to English upper-class boarding schools such as Harrow.

British officers brought the game to Pakistan, Egypt and India. Many of the world's best players, including the Khan family, continue to come from those former British outposts.

The American game also has monied associations. The Rev. James P. Conover built the country's first court, in the 1880s, at the St. Paul's School, a posh prep school in Concord, N.H.

But 100 years later Talbott, the sport's exemplar, is earning what obscure offensive linemen make in the U.S. Football League.

"We want to spread the game around with things like portable, see-through courts so more people can watch," says Talbott. "But it may take a while for it to get as big as tennis or even racquetball. It's a special kind of thing."