In their other lives, they are doctors, mortgage bankers, real estate brokers, business owners, lawyers or police officers -- a disparate collection of individuals from around the Beltway.

But when they are doing what they love best, they are polo players.

From late May until mid-October, while other Washingtonians are cheering the Orioles, or hitting golf balls, or trying to get Redskins tickets, these several hundred residents are spending every free moment on the area's polo fields.

In Poolesville, in Middleburg, and on the Mall, in league matches and tournaments, their many hopes and aspirations are narrowed to one: to ride up the field in simultaneous control of their horses and of a small white ball until that moment when they smack it cleanly, perfectly, through the opponent's goal.

"There's an excitement in playing the game that can't be duplicated in any other way," said Alan Nash, a 42-year-old Fairfax mortgage banker who has been playing organized polo for eight years. "The attempt to control a 1,000-pound animal at a speed {of 35 to 40 mph} while trying to athletically address a ball and coordinate with three other players on a team" is a never-ending challenge, he said.

"I don't know, I really don't," said Julio D'Angelo, of Potomac, owner of a courier service and sponsor of a polo team, when asked what makes him play polo four to five times a week during the season. "I can tell you I can't quit . . . it's a disease. It's very powerful. It's a way of life. I haven't met anybody ever who has started playing and then quit."

This week, polo enthusiasts such as Nash and D'Angelo are following the game's premier American event: the U.S. Polo Association Open in Lexington, Ky. At least one team of local residents, the Muldoon family, of Montgomery County, is competing in the event. The Muldoons own and operate the Potomac Polo School and Potomac Polo Club in Poolesville, one of this region's prime areas to learn, play and watch the game of polo. Charles Muldoon, director of the school, is among the country's top players.

A player such as Muldoon, who learned the game in childhood, is a rarity in the Washington area. Most players are well into adulthood when they become addicted -- because that is the time when they can afford to play. That is also the time when the game takes its hardest toll on the body.

"I try to discourage other people from going into it," Nash said. "For someone in their thirties to start playing is very difficult. I can't stress how difficult."

But that didn't stop Michael Brooks, a D.C. police officer who mounted a horse for the first time three years ago, at age 32. He has taken lessons at the Potomac school, and is considering "a polo vacation," a week of intense instruction in Palm Beach, Fla.

Players say it takes that kind of commitment to play with any skill at all. You simply need more time, and money, than most people can devote to sport. Polo has often been called the sport of kings, largely because when the game was invented more than 2,000 years ago, only kings could afford to play.

"The only way to get out of polo is to be broke," D'Angelo said. "And the fastest way to be broke is to play polo."

That's why he encourages neither friends nor family, especially family, to participate: "It would become more expensive immediately."

D'Angelo owns 14 thoroughbreds, a trailer and a truck to transport them, and employs a full-time groom -- an investment of tens of thousands of dollars yearly. And because he sponsors a team, he said, "polo takes about two to three hours of telephone calls a day -- who plays, what field, what umpire -- it's a great deal of work."

Robert T. Do, 30, a Bethesda physician, can't afford to spend that kind of time or money -- but he can understand the concept. He maintains a full-time medical practice but still manages to play polo at least twice a week. And he owns four horses.

"It's a high . . . it's definitely a high," Do said. "It's the best game I've ever played."

After the game, he is always exhausted, but much of his work-a-day stress is gone, he says. And so far, his girlfriend has been very understanding.

"She accepts that {polo} is my passion," Do said. "She knows I have to do it."