It used to be you could get a quick lunch in an almost rural setting without battling traffic or fighting for a parking place in downtown McLean. Or what there was of a downtown McLean.

Nowadays, McLean's 210-acre central business district, officially dubbed the CBD, is bulging at the seams, an explosion prevented only by a comprehensive land use plan implemented by Fairfax County in 1975 and the enforcement efforts of the McLean Citizens Association.

In the past three years, office buildings have sprung up all over the area. With the offices have come workers--executives and professionals and their supporting staff. A well-dressed business crowd now jostles with McLean high school students for places in line for lunch at McDonald's. The quickest lunch in McLean may be a Baskin Robbins ice cream cone or a delicacy from the Giant gourmet food store.

So far a truce of sorts has existed among developers, retailers and residents of nearby neighborhoods, based on the CBD plan. That plan strictly defines the business district's borders, which run generally along Route 123 (Dolley Madison Boulevard) on the northwest from Chain Bridge Road west to Ingleside Avenue, south to Tennyson, east (one lot deep) along Whittier, north on Old Dominion Drive to Corner Lane to east on Chain Bridge Road.

McLean is a "state of mind, a crossroads that has benefited from the existence of clearly defined CBD boundaries," according to Ed Walton, president of the McLean Business and Professional Association.

Though Fairfax County does not have any current figures on the percentage of land developed or available for construction within the CBD, things are plainly getting tight.

Expansion of the business district is regarded as politically out of the question, so the issue has become the extent to which existing commercial areas should be redeveloped to accommodate greater density.

At present, the area's low-density environment, plus convenience and a prestigious-sounding address are among the factors that have lured consultants, accountants, lawyers, doctors and other professionals into the new buildings along the Elm and Poplar Street corridors as well as along Old Dominion Drive and Whittier Street.

April Young, director of the Fairfax County Economic Development Authority, calls the McLean business district "terrific. It's 15 minutes to downtown, it's an extremely attractive place to live and work."

Ross Collins moved his accounting firm to McLean from Falls Church for many of the same reasons others say they've made the move. "We thought it was definitely a growing area with many new businesses, convenient to Tysons and downtown," he said. Collins, who is building a home in Potomac Overlook, described McLean as a beautiful area in which to work and to live. His 16 employes occupy a 4,800-square-foot office facility on Beverly Road.

McLean is a late bloomer compared to other areas of heavy office concentration in Northern Virginia. "For a long time, property in the 1970s within the central business district wasn't appreciating, not keeping up with the consumer price index," explains William H. (Kip) Laughlin. He is the fourth-generation chief of Laughlin Realty, whose office in what long-time McLean residents call "the blue house" occupies one of the five points of McLean's main business intersection where Old Dominion Drive, Chain Bridge Road and Elm Street merge.

During the early and mid-l970s, residential real estate in McLean was a much better investment, Laughlin says. The 1980s brought a commercial explosion but commercial space "is still a bargain in McLean compared to Rosslyn and Tysons," Laughlin says.

Nobody wants McLean to be another Tysons. Civic Association President Ted Gray even speculates that McLean might still be a sleepy suburb if Tysons had not developed as such a retail and office giant.

Open land for commercial development within the CBD is virtually used up. Only three parcels are now ready to be built on, and there are plans for all three. Several others could be pulled together, but local developers say it will take someone with lots of money to come in and buy up individual adjacent tracts to create development sites.

Office space in McLean is currently available but Realtors say most of what's available is small spaces, the leftovers.

"There is space available at a reasonable rate," Professional Association President Ed Walton says. "About 18 months ago, there was concern that McLean was glutted with offices, A lot of the space in the Elm Street area hit the market in the same 12-month period. Now nobody is in trouble, nobody's financially hurting," he explains.

According to the spring update of Black's Office Leasing Guide for the Washington-Baltimore Metro Area, available space in McLean runs from $11 to $15.50 per square foot for full-service space. Projected rates for proposed buildings run as high as $17. Leasing rates in McLean compare favorably with those listed by Black's Guide for the Tysons area. Space there averages between $12.50 and $20, and a lot of that space is in high-rise, high-density developments ranging from six to 14 stories. Most space in McLean is in three- or four-story buidings or town houses. The McLean Office Center is seven stories tall, and the nearby Fleetwood Building eight stories.

Retail space on the street floor of a building under construction at the corner of Elm and Poplar will lease for between $18 and $24 a square foot, according to Irv Ross, whose accounting firm of Ross, Langan and McKendrie, along with the building's general contractor, Jack Bays Inc., will occupy a large part of the building's 24,000 square feet of office space.

"We are running out of room, but there's no plan afoot or desire to expand the CBD," says Fairfax County Supervior Nancy Falck. She has moved her office into the CBD on Poplar Street because of expansion at the county's annex on Balls Hill Road outside the CBD.

What does the future hold for McLean's central business district? There is concern over how a block of land along Whittier, Laughlin and Chain Bridge Road might be developed. However, the lots are now individually owned, with many owner-occupied and not up for sale. Consideration is being given to an idea developed by McLean architect Susan Notkins for a village-type plan combining retail and residential space.

The plan would offer street-level retail space with living quarters above, according to Robert Young, who isn't involved as a developer but as a member of the McLean Planning Committee, a group of residential property owners, developers and business leaders named by the county to review all proposals for the CBD.

Presently, Fairfax County doesn't even have a zoning category that would permit such development.

"The residential over retail doesn't fit McLean's image," Gray says. "It may have worked in the Old World, but you won't find anybody here who'll want to live over the retail. I don't think it would work economically."

There is also talk of the City of McLean, according to Business and Professional Association President Ed Walton. But he says most residents understand the complications of any such move. "We'd have to have Tysons inside the City of McLean, and Fairfax County isn't about to let that happen," Walton said.

Fairfax County planner Ken Doggett doesn't foresee any great push to expand the present CBD boundaries.

He argues that "there's not a shortage of land in the business district. A lot of the present land is underdeveloped." Translated into layman's language, that means the possible redevelopment of existing shopping centers.

Walton also predicts "upgrading of existing centers. Some are getting a bit of age on them. We'll need to start over and/or update. There will be a need for that." Gray said Civic Association leaders, however, don't think the need for additional retail space is as great as commercial people say.