Everything may look businesslike and serious when you take a tour through that house at 16th and Pennsylvania, but hidden discreetly behind some trees on the South Lawn lurks another reality: the White House Country Club.

"Isn't it beautiful?" murmured the khaki- and linen-clad guests at the first Nancy Reagan Drug Abuse Fund tennis tournament Saturday as they wandered from the White House tennis court across the rich grass. Beneath a red-and-white striped tent waited men in tuxedos and glasses of lemonade. Brooke Shields, Tom Selleck, Veronica Hamel, Ricky Schroder, Tracy Austin, Cliff Robertson, Dina Merrill, John Forsythe, Secretary of State George Shultz and other stars of stage, screen, tennis court and Cabinet dotted the lawn like so many well-placed, expensive statues.

"It's great to see people who have reached a certain level of recognizability who care about this," said Redskins quarterback Joe Theismann, holding a tiny tea sandwich and standing next to Cathy Lee Crosby, who played in one match with Sen. Paul Laxalt (R-Nev.).

Not everyone was as immediately recognizable as Theismann and Crosby, who served as umpires in the first match, but if the faces were unfamiliar, the affiliations were not: Citicorp, General Motors, United Technologies, Prince Manufacturing, Occidental Petroleum. Most of the 200 sitting in the court-side bleachers were representatives of nine corporations that donated $50,000 each to the newly established drug abuse fund.

For that, each corporation got about 10 people into a Saturday morning brunch at the Hay-Adams, an afternoon of six 20-minute doubles matches with players like Shultz, Interior Secretary John Herrington, Rams quarterback Jeff Kemp, tennis pros Pam Shriver and Roscoe Tanner and spectators like Ronald and Nancy Reagan. And a postmatch White House reception.

They also got to listen to court-side banter.

"I'm not doing anything major this summer," said Shields, perched in a high umpire chair, her legs crossed demurely below her white miniskirt. "My book will be coming out soon and I'll be promoting that. It's about the last year of high school and the first year of college -- the transitional period many people my age have to make. It deals with careers, grades, schools, boyfriends, exercise."

"Brooke says I'm in it," said Selleck, Shields' co-umpire.

Shields giggled. The corporate sponsors laughed along. The day wound on.

There was the predictable string of tennis-comes-to-Washington jokes:

"Stately serve, there, Mr. Secretary," Shriver complimented opponent Shultz.

"Do you work?" umpire and pro golfer Hollis Stacy asked Laxalt. "Your serve is awfully good."

"We hoped justice would prevail," said FBI Director William Webster at the reception, "but sometimes the system doesn't work." He and partner, actress Veronica Hamel, had lost their match to actor Robert Duvall and Atlanta Falcons running back Joe Washington.

And the predictable euphoria:

"She's a real heavy hitter," Webster continued, referring to his partner. "Great fun and beautiful -- a beautiful player and a beautiful person."

"Isn't this a five-star event?" asked former White House aide Joseph Canzeri, one of the organizers of the day's events, which were expected to net $375,000. "When you do any kind of event you need a hook, and the president and the first lady aren't a bad hook. And the White House on top of that, and Tom Selleck and John Forsythe. It's important something like this is small and intimate. As we say in the business -- it's a grabber."

And it was a chance for friends to catch up:

"I feel I am getting quite close to her," said Shields of the first lady, with whom she has appeared and filmed an antidrug commercial. "I feel we have a good understanding. We don't really need to say much. I can just look across the room and she'll smile that I'm taking the right track."

Harry Gray, chairman of United Technologies, spoke with the president for a while and said, "We were just telling him about some old friends. We both belong to a club together, which he hasn't been able to attend since he was elected. What I think is wonderful is he keeps his contacts up with people in the Bohemian Grove -- he writes them personal letters. And he writes them himself. His staff doesn't do it."

The air of intimacy was as delicately cultivated as the flowering bushes around the court.

The children of Canzeri, former White House deputy chief of staff Michael Deaver and Republican National Committee Chairman Frank Fahrenkopf Jr. served as ball boys and girls. The audience included Jeff Kemp's father, Rep. Jack Kemp (R-N.Y.).

"I know you must be tired and hungry," Nancy Reagan told the crowd on the court after Selleck and Shields presented Prince racquets to the first lady and president, neither of whom plays tennis. "So my new tennis partner and I would like to ask you if you'd like to come inside for a little buffet."

During the reception, Nancy Reagan sat for more than half an hour on the balcony overlooking the South Lawn chatting with the Shultzes, Selleck, Robertson and his wife Merrill. After making the rounds, Reagan joined her and leaned casually on the arm of a chair. Guests lined up behind him and had friends take pictures of their smiling faces above the president, who was deep in conversation and seemed oblivious to the click of camera shutters.

And people kept kissing. A camera-toting U.S. Information Agency Director Charles Z. Wick kissed Merrill. Nancy Reagan kissed Selleck. At the reception, she kissed him again.

"You don't know how good this makes me feel," she told the guests as she thanked them for their patronage. "We're not going to solve the drug problem alone. It takes our energy, our dedication, our commitment and letting our young people know we care for them -- we love them."

Then she presented checks for $50,000 to representatives of two drug treatment centers and kissed several former drug addicts.