Haig Tufenk remembers the incident vividly. He was in the chair, umpiring a third-round match between Guillermo Vilas and Marty Riessen at the Washington Star International tennis tournament in July 1979.

Vilas, the top seed, was also the only real drawing card. There was a close call on a serve and Vilas disagreed with the line judge. Tufenk did not and Vilas got angry. He argued. Tufenk held his ground. Vilas demanded the referee. Then he directed an obscene comment toward Tufenk.

Tufenk had to sit in the chair and listen. He could not default Vilas. If he did, he would incur the wrath of the fans and the promoters. So he took it.

So why would anyone want to be a tennis official?

"Good question," Tufenk said the other night after working as a line judge in Vilas' third-round match in the U.S. Open. "You get into this because you love tennis, probably because you once wanted to be great and you weren't and because you've got enough ego that you love being out there, you know, show biz.

"Once people were umpires just to be around players, to go to the cocktail parties and hang around with them. Not now. We're not even allowed to fraternize on the men's tour under the rules. Now you have to do it because you have pride in what you're doing. And you better be good."

Whether tennis officials are good enough in this, the 14th year of open tennis is a question now frequently raised. Many players claim the quality of officiating hasn't kept up with the quality of play.

Quietly, many officials, while pointing out that officiating has improved greatly, agree.

"What do you expect when people are being paid a per diem of $37.50 a day and that's it?" asked umpire Al Friedman. "It's like taking an ad the week of the Super Bowl asking for six guys to pay their way to Los Angeles to get $37.50 per day to referee. Paid officials are coming in the future but someone's going to have to come up with the money."

The officials here consider themselves professional even though they are unsalaried. Each has been to an officiating school and to clinics. Each must receive a certification card from the USTA annually.

But, officials admit, these are not the 196 best tennis officials in the country. Open officials are chosen by region and some weak ones get here because some sections do not have enough good officials.

One weak official can ruin a match. "If you have a good crew and a good umpire you aren't going to have any problems," said Bill Bigelow, chief umpire here and the man who chooses most officials and assigns them to matches. "We look for experienced officials here. If they don't know what they're doing when they get here, we don't want them. We're not here to teach."

Bigelow readily concedes there are some umpires he would not want in the chair when John McEnroe is on the court. "Matching an umpire with a player isn't a lot different from matching a man and a woman," he said."

Bigelow tries to be certain that no umpire is assigned to the same player twice during the tournament. Memories are too fresh then.

Throughout the tournament, Bigelow has a crew of evaluators watching the officials. There are 35 chair umpires who work the men's and women's singles and doubles matches. Line judges are divided into five-person crews. The crews are quite competitive.

The umpires are also supportive. They often can be seen consoling one another in their lounge after a tough match. "It eats my guts out when I'm out there and I see another official getting abused by a player," said Doug Russell. "I'm not going to say or do anything out there but once we get in here, I'll be sure to tell him he did the right thing."

Most officials also insist that when players argue a call, the players usually are wrong. They point to testing done on people in motion. They show that when someone is moving, it is more difficult to make a call than when he is standing still.

Still, all admit they are not infallible. Friday, when Andrea Jaeger, known on the tour as a noncomplainer, yelled loudly that she was done in by bad calls, many of the officials went out of their way to look at replays.

The consensus: Jaeger was right. "If the umpire had been on the ball, he would have corrected a couple of obvious bad calls," one umpire said. "But he didn't and that's really a shame."

"We have doctors, teachers, lawyers, goverment workers, you name it, working here," he said.

"One of our top officials is Charlie Beck; he's a doctor," Bigelow said. "You think he's going to give up his practice for $37.50 a day?"

Three years ago the men's Grand Prix tour hired four supervisors to oversee the officiating and to impose penalties for misbehavior on the players. Fines now are swift and often substantial.

Last year, the number of officials used on a match was cut from 13 to six, a move designed to make them more alert with more to do. All the officials say the days are over when a Grand Prix supervisor will tell an umpire not to default a star player in order to keep him in the tournament.

"It improves every year," Bigelow said. "But I'll tell you something, if you can get those umpires and line judges to tell you why they do this, tell me, because I sure don't know."