The lawyers call it "supercase:" the United States versus American Telpehone and Telegraph Co., the largest antitrust suit ever filed in this country.

By the time it is over, taxpayers and telephone customers may be stuck with a $1 billion bill, the potential cost of resolving the legal warfare between the federal government and the largest corporation and private monopoly in the nation.

Millions of documents, thousands of government and AT&T employes, hundreds of specialized attorneys, and an enormous support apparatus have become involved in the seven-year-old lawsuit in U.S. District Court here, as the combatants struggle with the question of how and whether the AT&T empire should be dismantled.

Meanwhile, the case goes on, expanding beyond the bounds of the courtroom, becoming a textbook and a history in the writing, a story of how a centuries-old judicial process attempts to deal with rampant teahnology in a society gone document-and lawyer-crazy.

An event last year shows how complex the supercase has become. When trial Judge Harold H. Greene ordered both sides to narrow the 1,872 pages of government accusations, both sides sat down around a single table. Within weeks, they had taken over the entire second floor of the Skyline Inn in Southwest Washington, more than 300 attorneys and paralegal aides in 29 rooms, smothered in documents.

In the years since the Ford Administration filed the suit, the judge originally assigned to the case has died, AT&T's chief legal counsel met and married a Washington lawyer, children have been born to attorneys working on the case, AT&T employees have moved from Chicago and New York City to Washington, and a few government attorneys have spent their entire federal careers working only on this case.

The case has taken its toll in personal lives.

"The strain on marriage . . . is unbelievable," says AT&T lawyer Pete Lumia. "There's a standing joke among the AT&T attorneys. This is the biggest antitrust case of the century, and when it's over, all our wives are going to file the largest class-action divorce suit of the century."

The statistics surrounding the government's attempt to dismember AT&T are simply "mind boggling," says government attorney Mike McNeely. Consider these:

Before the case even reached the trial stage last February, AT&T had spent $293 million preparing its defense, or $40 million more than the District of Columbia plans to spend operating public schools this year. The Justice Department, which lists the case as a separate budget item, has spent $12 million, and expects to spend $4 million more this year.If the case is appealed, chief AT&T lawyer George Saunders claims costs could hit $1 billion.

So far, the government and AT&T have inspected, copies or computerized an estimated 20 million documents -- enough, if put into book form, to rival the entire 26,367-volume Philosophy-Psychology-Religion Division of the Martin Luther King Library here. At one point, AT&T assigned 1,000 employes in Orlando, Fla., to examine memos, reports and other documents for the case. The corporation has rented three floors of a Washington office building to house its document library.

The government hired outside consultants to show it how to process paper. It borrowed thousands of key documents from AT&T's competitors, who also are suing the telephone company, and hired 50 temporary employees to work around the clock shuffling paper. Pointing toward two huge copying machines, government attorney Peter Kenney suggests: "These are the two busiest copiers in the entire federal government."

At various times, up to 3,000 AT&T employees have worked full time on the case, including 300 in-house and private attorneys. The company has moved more than 125 attorneys, paralegals and other aides from Chicago and New York City to Washington, where most are staying in fashionable Washington hotels, including the Madison, where Saunders has lived in a deluxe two-bedroom suite from November. Some have rented apartments, and at least three AT&T attorneys have moved their families here.

Badly outnumbered, the government attorneys call themselves the Green Berets: "A few good men doing a dirty job." Three different teams of attorneys have worked on this case since it was filed. Fewer than 10 lawyers originally filed it. Now there are 40 government attorneys. Most are new, full-time employees added to the payroll specifically for this suit.

"Overall, this case involves maybe 80 different legal questions," says Saunders. "What you really need is a fantastic but easily erasable memory, so you can soak in everything that you are told and is important, and wipe it clean and start anew the next day. It's an incredibly difficult task for a judge to comprehend it all."

It took both sides six years just to prepare for trial. The government wound up the four-month presentation of its side of the case in June, after calling 93 witnesses. AT&T plans to call at least 400 witnesses when it begins its scheduled four-month-long defense Aug. 3.

"It's impossible to tell how many hours you have to put into this case," says Lumia, who has been married 23 years, and whose wife and two youngest children recently moved to Washington for the summer from a New York City suburb. "Time blurs together; only the court deadlines matter. You find yourself looking at your calendar watch to figure out what day it is.

"I'd catch the red-eye [late shuttle flight] to New York two or three Fridays a month," he said. "I'd get home about 9 p.m. and be dead tired. Saturday, my wife would want to go out, but I'd been eating at restaurants every day. I wanted to stay home. Sunday afternoon, I'd be gone."

His family had trouble planning their weekends. They never knew if he would be home. Little things began to bother him, Lumnia said, like when his garden became overgrown with weeds. A former town council member and mayor in suburban New York, Lumia had to forget community affiars.

"People would ask my wife where I was, and she'd say Washington. A few thought we weren't getting along," he recalls.

He lost track of office gossip, and learned one day that AT&t had hired a new lawyer to do his former job.

"It [the case] becomes a life unto itself, a world unto itself," he said.

Pushed together constantly, undergoing the same pressures, attorneys for AT&t and the government have become friends.Last month they held a picnic, and government attorneys showed up outfitted in bright yellow T-shirts bearing the slogan, "Reach out and crush someone" -- a twisted version of the jingle in the AT&T commercial.

But tension remains.

"This has not been fun," says government lawyer McNeely. "The only contact that I want to have with the telephone company after this is that telephone unit on my desk."

After the picnic, some government employees complained. They had had to pay $10 to $15 per person to cover the cost of picnic beverages. AT&T supplied the costliest item, the food, but their employes came free. The telephone company simply hired Ridgewell's Cateers, one of the city's most prestigious, to bring the goodies. Ridgewell's also regularly supplies finger sandwiches to AT&T attorneys at lunchtime at the courthouse.

"It offends me that part of my telephone bill is going up because of so much unnecessary padding," says Kenney, "but there are no good places to eat near the courthouse and if they all came to the greasy spoon where we eat, we'd never get served."

Despite the headaches, years of work and taxpayer's money, the case could end next month if Judge Harold H. Greene rules in favor of a 500-page brief filed by AT&T last week. Saunders claims the government hasn't proved a single accusation. Such a dismissal by Greene is considered unlikely.

Even so, the suit still could end abruptly if President Reagan orders the Justice Department to end its prosecution. Defense Secretary Caspar W. Weinberger has urged Reagan to drop the suit, and Commerce Secretary Malcolm Baldrige says the administration disagrees with the Justice Department's goal of divesting AT&T.

This makes the government's trial team angry, but few will complain on the record about Reagan. Kenney defends the government's use of tax money to go after the company.

"If we don't try to correct a wrong because it costs money or is going to take a long time, then we are saying that big companies don't fall under the antitrust laws," he says.

Saunders claims that the government's case is ridiculous and never should have been filed. But something else about the supercase bothers him: AT&T and the government have shown how a supercase can be brought to trial. They have drawn a road map of sorts that other courts already are adopting. And, Saunders fears, the AT&T supercase "is just the beginning."

"In our zeal for law and due process of law and the belief that everyone has a right to a day in coiurt," he contends, "we are going to destroy American industry."