Some are calling it the birth of a portion of Fairfax County. Some see it as the end.

No matter which characterization is embraced, last week's decision by the Fairfax Board of Supervisors to locate the county's new $83.4 million government center on wooded, rolling land near I-66 establishes the area around the Fair Oaks shopping mall as Northern Virginia's newest development hot spot.

For the developers who are already sinking hundreds of millions of dollars into the 5,300 acres surrounding Fair Oaks, the news couldn't be better. The new government complex, they say, is merely the latest catalyst helping to mold the Fair Oaks area as a hub for commercial and residential development.

For a once-sleepy area that only 30 years ago had more cows on dairy farms than people in the community, the current development numbers are staggering. According to figures compiled this week by The Washington Post, a total of 12.4 million square feet of office space has either been completed in the past year or is planned for construction over the next several years -- a figure equal to nearly four Pentagons.

In addition, at least 6,000 residential units are planned or under construction. A total of 1,700 acres has been or will be developed -- an area nearly 12 times the size of the Mall between the Lincoln Memorial and the Capitol.

But for long-time residents, the government center, the office towers and the new packed-in residences all signal an end to a way of life. They point to Tysons Corner, with its congested, bumper-to-bumper life style, and claim it will be only a matter of time before Fair Oaks is just as crowded.

"We sat here and watched what happened at Tysons. Now we're going in the exact same direction," said Shirley Swiney, a resident of Fairfax Farms, a subdivision of 84 modest homes just north of the shopping mall. "There's no way we can remain the same. We're just being snuffed away back here."

Developers react angrily to the suggestion that the Fair Oaks area is a mirror of Tysons. They contend that despite current traffic woes experienced by commuters, Fair Oaks will be a well-planned mixture of housing and offices. That mixture, however, has not been voluntarily offered by developers, but mandated by a county that has been inundated with pleas from its residents to contain office development.

Nonetheless, there is little stopping the building at Fair Oaks. Most deals have already been struck. In other cases, entire neighborhoods are being considered for rezoning that would permit much greater densities than are currently allowed. Such rezonings could give developers the impetus to buy homes in a neighborhood, raze them and construct 15 or 20 town houses on a lot that had held only one home.

Fairfax County figures also show the area's growth, particularly as an office locale: commercial space either already built or approved for construction jumped 38 percent from 1985 to last year.

Residents and developers have had a notion of Fair Oaks' future since the mid-1970s, when the county termed it a "growth area." But few of them, including county planners, envisioned the extent of the boom.

Until about seven years ago, development of the area was limited to a scattering of small office buildings and detached houses. In 1980, the Fair Oaks shopping mall, with its 188 retail outlets, opened for business. Earlier this year, another 27 outlets were added to the mall, further fueling the rivalry between Fair Oaks and Tysons for the wallets of Northern Virginia's indoor shoppers.

Since opening, the Fair Oaks mall's sales volume has risen 10 percent or more each year. "And with the growth of the area, I just don't see that stopping," said Gil Brooker, the center's general manager.

The shopping center gave birth to several office buildings and a hotel, which popped up on land surrounding the mall. A wide range of groups has been attracted to the area's office buildings, including architectural and law firms, defense contractors and other government-related firms, mortgage companies, banks and health care companies. This week, Mobil Corp. announced that it was leasing all 12 floors of a new, 215,000-square-foot office building overlooking the shopping mall.

"This has become a very exciting relocating area," said Brian F. Tucker, vice president of leasing for the Evans Co., which developed the office tower Mobil leased.

Reshaping the Rte. 50/I-66 corridor as much as any project is Fair Lakes: 620 acres under development that, when finished over the next 10 years, will hold more than 5.1 million square feet of office and hotel space in 35 buildings. In addition, 1,300 residential units are planned at Fair Lakes, which is being developed by Hazel-Peterson Cos.

Fair Lakes has attracted the Fortune 500 firms of TRW Federal Systems Group and Mohasco. Hyatt has also selected the area for a hotel.

Other major projects under way or planned in the immediate shopping center vicinity include the Fair Ridge housing subdivision, the Centerpointe office complex, the Gateway Center office, hotel and residential development and the Penderbrook housing subdivision.

New home prices and rental rates in the blossoming Fair Oaks area are not cheap. At Penderbrook, new homes cost up to $300,000, while monthly rents range between $600 and $1,000. Existing home prices range from about $85,000 for town houses in the Dixie Hill subdivision to $190,000 in Fairfax Farms.

This week the talk around the Fair Oaks area was of the coming of the county's new government center complex, approved by the supervisors after a decade of debate and legal wrangling. The government offices planned for 100 acres of land between I-66 and Lee Highway will include nearly 1 million square feet of space and are expected to house hundreds of county employes.

In return for the new county facility, the supervisors agreed to give the project's developers, the Charles E. Smith Cos. and the Artery Organization, $41.2 million in cash and other compensation. In addition, in what critics have called a sweetheart deal, the county gave approval for the developers to build a massive mixed-use project on 116 acres of nearby land. More than a million square feet of office and hotel space is planned for that area, as well as 600 residential units.

Other developers in the area, who claim they are having a tough time obtaining county approval to build additional office space, criticized the way in which the government center complex was approved.

"I think it's ridiculous," said Michael Windsor, regional partner with the Property Corp. of America, a major development force in the Fair Oaks area. Windsor's group is attempting to rezone the Random Hills residential neighborhood so the development firm could construct office buildings and housing with greater density. That application will be heard by the county's Planning Commission on Sept. 9.

Despite vocal criticism by some area residents and county planners against rezoning the 85-acre neighborhood, Windsor said he "believes the area is better suited for office and hotel use."

Echoing the views of other Fair Oaks developers, Windsor disputed the notion that development in the Fair Oaks area has run amok.

"Sure we've got some transportation problems," the developer said. "You hear a lot of criticism about growth, but there are a hundred other cities ... that would like to have the kind of prosperity we have."

In a year of county elections, when concern about growth has become a major issue among Fairfax residents, some critics believe Fair Oaks ought to be the battlefield on which the developers are stopped. But county officials maintain that Fair Oaks is at least being planned, unlike much of the Tysons area.

"I believe the {county} does have the mechanisms to contain development" in the Fair Oaks area, said Thomas Pauls, a land-use planning analyst in the county's comprehensive planning office. He said one of the central issues facing planners concerns the area's land use.

"We want to ensure that the height and bulk of the development won't destroy nearby existing neighborhoods," Pauls said. "We're trying to make sure what is under construction and what is planned is compatible with what's already there."

Developers contend that what they are building has only improved Fair Oaks. "All the developers are extremely pleased with what's going on out here," said Daniel Keusal, senior vice president of Parkford Inc., developers of Penderbrook, an 1,800-unit subdivision under construction near Fair Oaks. "I don't know of any bad news out here."

Long-time residents, who have witnessed their quiet lifestyles give way to the onslaught of congested highways and higher property taxes, strongly disagree.

"We've got the problems inherent with progress," said Fairfax Farms resident Swiney, who is also president of her neighborhood's community association.

Last year, most residents in Swiney's subdivision decided to sell their homes en masse to two developers who were planning a large-scale residential development. But the deal was scrapped when the county refused to rezone the neighborhood to permit the greater density.

"The only reason we made those waves was because our quality of life has been eroded away," Swiney said.

Aside from the traffic woes and construction noise that have transformed the Fair Oaks area, Swiney said the development has spawned a major flooding problem in the small streams running through the Fairfax Farms neighborhood. The problem didn't exist before the shopping mall was built seven years ago, she said.

As a result of the flooding, which has occurred 12 times in the past year, many of the subdivision's residents are unable to get to or from their homes until the water subsides from the streets.

Now the residents of the close-knit neighborhood, where a dairy farm once stood, say they are willing to sit tight for awhile. Unlike the homeowners of two other smaller subdivisions in the area, they are no longer strongly pushing for the mass sale of their neighborhood.

"We just want to be left alone," Swiney said.