Martina Navratilova and Pam Shriver, doubles partners and friends for so long that they have trouble becoming opponents, turned a normal tennis match into a bizarre comedy routine tonight at Madison Square Garden.

Navratilova, the top seed in the $500,000 Virginia Slims Championships, had little trouble with unseeded Shriver, winning, 6-2, 6-4, to advance to Saturday's semifinals. She will face third-seeded Hana Mandlikova, who defeated seventh-seeded Zina Garrison, 6-3, 6-4, in tonight's first match.

In the other semifinal, unseeded Kathy Rinaldi, who will turn 18 Sunday, plays No. 5 Helena Sukova.

Try as they might, it seems unlikely any of them will be able to provide an encore for the Navratilova-Shriver schtick.

There were primal screams from Shriver, who recently returned from a three-month layoff with a new, wavy hairdo, and jokes from Navratilova, who is wearing wire-rimmed glasses for the second consecutive tournament to correct nearsightedness. They knocked down the Slims' court-side signboards three times, once on purpose, and Navratilova even sat in a spectator's lap.

That's not all. With the match all but decided in the second set, one of the 13,058 spectators let out a ferocious sneeze in the upper deck.

"Bless you," Navratilova yelled.

Shriver, never one to be outperformed, immediately began to wipe her cheek, as if the culprit were sitting in the front row, too close for comfort.

Navratilova broke up.

"You know I can't play when I'm laughing," she yelled to Shriver.

Perhaps that was Shriver's strategy.

Tennis was merely a sideshow in this match by the time they reached the eighth and final game of the first set, with Navratilova leading, 5-2. Quickly, Shriver jumped to a love-40 advantage, with three break points. Just as quickly, she frittered them away, and Navratilova was serving for the set.

Shriver, as she is wont to do, yelled at herself and hit her racket.

Navratilova, off Shriver's return of service, hit a forehand drop shot that Shriver reached on what appeared to be the second bounce for a winner past Navratilova.

"Deuce," said umpire Steve Berlin.

"I don't think I got it," Shriver said, looking toward her coach, Don Candy, in the stands.

Time for a meeting with the umpire.

"Don said I didn't get it," Shriver pronounced to the world. "I'm fast, but not that fast."

She overruled the umpire.

What's a set point between friends?

"It was like Hagler-Hearns out there," Navratilova would say. "Real stuff out there. Really, we both play better when we're relaxed."

Shriver could not have been any more relaxed, but it didn't help. She broke Navratilova's serve just once, to get even in the first set at 1-1.

"I was struggling to break serve," Shriver said. "Instead of breaking serve, I thought I'd try to have some fun."

The high point of the hijinks occured in the seventh game of the second set. When Navratilova dove for a shot and lashed a forehand winner down the line, she couldn't stop herself and plowed into the Slims' court-side sign board and into the first row.

Moments later, on a point Shriver won, she did it again. Instead of coming right back to the court, Navratilova plopped into the lap of an unsuspecting fan for a moment, then helped revive the sign for the second time.

Meanwhile, on her end of the court, Shriver walked over to the matching signboard and kicked it over.

"I couldn't believe it," Shriver said.

Neither could anyone else.

Shriver, who has had horrendous results against Navratilova, winning only three times in 23 matches, said she could not afford to make mistakes if she was to have a chance.

Instead, she called her performance "cruddy" after the midway point of the first set.

She had kinder words for Navratilova.

"She's playing better I think now than the last time I saw her in New Jersey (last year)," Shriver said, which are not kind words for the rest of the field.

Most immediately, that means Mandlikova, who weathered a difficult serving night (only 45 percent of her first serves went in) to defeat erratic Garrison.

Mandlikova survived three break points in an 11-minute game in the first set and won it, and eight break points in an eight-minute game in the second set to advance to the semifinals of the Slims Championships for the first time in five tries. The other four times, Mandlikova lost in the quarterfinals.

"If you really want the truth, I've never played well in the Virginia Slims tournament," she said. "I'm happy with this."