The clinking of champagne glasses could be heard in antitrust law offices all around Washington Tuesday night. There was reason to celebrate.

July 18 was the fifth anniversary of the famed "Exxon suit" filed by the Federal Trade Commission, charging the nation's eight largest oil companies with "anti-competitive practices." It's called the "Exxon suit" because Exxon was listed first on the complaint - it's the biggest.

And after five years, the FTC has gone nowhere - the agency's still in the discovery stage and has not yet received one "substantive" document from any of the oil companies.

Unquestionably, this case has become one of the great legal disasters in history. After the initial filing of the complaint, the case foundered for years in a monotonous filing of papers.

Then, in February 1976, the FTC filed an 1,800-page request for "substanative document discovery," from the oil companies. The defendents said it would be impossible to comply with such a huge request and appealed to the commission.

In November 1976, an FTC administrative law judge agreed with the oil companies, calling the request, and the case that would grow out of it, "unmanagable."

But at least he did order the oil companies to hand over some "nonsubstantive" materials.

In January 1977, the FTC lawyers appealed to the full commission to overturn the administrative law judge's ruling.

That request sat around until September 1977, when the FTC lawyers filed another pleading with their own commission stating that they had changed their mind, and decided they didn't need all of the documents they asked for in their 1,800-page request.

Instead, they said they would refile a request for documents that would be less burdensome.

Then last Jan. 12, the FTC lawyers filed another request for documents, which the oil companies again challenged.

On May 10, the FTC filed yet another request, this time for information concerning the computer systems used by the oil companies. Again, the oil companies are fighting that request.

Meanwhile, the Department of Energy's Office of Special Counsel, in its investigation of oil company pricing regulations, has already received access to the computers of one oil company - Shell - and has asked for others. And the Office of Special Counsel has only been in existence for about seven months.

The late Sen. Philip A. Hart (D-Mich.), had originally asked the FTC to undertake the investigation in 1970. Elated when the complaint was finally filed, even Hart may have underestimated the length of legal wrangling that would be involved when he said:

"The sad part is that we won't get a verdict - and relief - for 8 to 10 years. The FTC has to prove not just monopoly power, but anticompetitive behavior. This will mean a search of millions of documents to confuse everyone."

Meanwhile, many of the practices alleged in the FTC complaint to be anti-competitive still go on.