Kohlschreiber, ranked 29th in the world, refused to wilt in a match that last nearly four hours and came away with a 6-4, 3-6, 7-6 (9), 6-7 (3), 8-6 victory over the sixth-ranked American.

"That was just amazing. It's the best that happened to me in tennis," Kohlschreiber said. "I enjoyed every second. It was just high-class tennis from both players."

Roddick came into the Open on a hot streak, having led the U.S. team to the Davis Cup title and then winning a warmup exhibition at Kooyong last week. But in a match in which both players were on their game, Kohlschreiber was at his best in reaching the fourth round of a Grand Slam for only the second time.

He next faces 14th-ranked Jarkko Nieminen, who ousted Roddick's good friend Mardy Fish in four sets.

Earlier, second-ranked Rafael Nadal and fourth-seeded Nikolay Davydenko advanced in straight sets. Nadal next plays No. 23 Paul-Henri Mathieu, who had a five-set victory over Stefan Koubek, while Davydenko meets fellow Russian Mikhail Youzhny, who beat No. 20 Ivo Karlovic. Eighth-seeded Richard Gasquet also advanced for a meeting against unseeded Jo-Wilfried Tsonga.

On the women's side, top-ranked Justine Henin, defending champion Serena Williams and 2007 runner-up Maria Sharapova won their third-round matches.

The fans were still buzzing from Australian Casey Dellacqua's upset of 2006 women's champion Amelie Mauresmo when Roddick and Kohlschreiber took the court with the roof closed over a packed Rod Laver Arena due to a light rain.

They got a display of great tennis and high drama. Roddick pounded a personal best 42 aces — to 32 for Kohlschreiber — and compiled 79 winners to just 24 unforced errors while overcoming several close calls that left him angrily criticizing chair umpire Emmanuel Joseph of France.

Kohlschreiber was even better with 104 winners and 33 unforced errors.

The match ended at 2:04 a.m. after 3 hours and 53 minutes.

Roddick dropped only six points in five service games in the first set, but four came as he was broken at 4-4. Kohlschreiber, generally trying to pick on Roddick's backhand, was even better on serve, dropping only four points in five games.

He escaped his first trouble by rallying from 0-40 in his opening service game of the second set, but Roddick finally broke through with his next opportunity to take a 3-1 lead, then preserved the edge by holding serve the rest of the way.

Roddick had just one unforced error in the second set and four in the third but lost the tiebreaker when Kohlschreiber ripped a forehand service return for a winner to go up 10-9 and Roddick sent the next service return long, smashing his racket as he headed back to his chair.

Roddick remained irritable the rest of the match, particularly after he thought he had won a service game at 5-5 in the fourth set but Kohlschreiber challenged the line call and won the point. Roddick complained loudly to Joseph that the point should have been replayed, then still held.

"I've had enough of this umpire," Roddick said at the changeover.

With coach Jimmy Connors shouting encouragement, Roddick ran off the last four points of the tiebreaker to even the match at 2-2.

Roddick saved four match points while serving at 4-5 in the fifth set — three with aces. But he couldn't come back after Kohlschreiber ripped three winners as Roddick served at 6-7, then a forehand crosscourt into the corner for match point that Roddick could only watch.

After routing Lindsay Davenport in the last round — a match that Sharapova said she prepared for as if it were a final — she seemed puzzled and frustrated that she couldn't put away fellow Russian Elena Vesnina until she finally pulled it together and ran off the last nine games for a 6-3, 6-0 victory.

"I really tried to keep the intensity I had in the previous match, but that's always difficult," said Sharapova, who next faces another Russian, No. 11 Elena Dementieva, a victor over Israel's Shahar Peer.

There were no high, looping moon balls when Williams faced Victoria Azarenka, just power tennis. And when it comes to power, Williams may be the best, running her record to 26-1 at Melbourne Park since the start of 2003.

Her serve was working particularly well, with 15 aces and a stretch of seven service games in which she yielded only six points.

"I feel pretty good about where I am," she said. "Hopefully, I'll peak later in the tournament."

Williams next faces 12th-seeded Nicole Vaidisova, while Henin puts her 31-match winning streak on the line against Taiwanese qualifier Hsieh Su-Wei.

Former No. 1 Mauresmo, who has fought nerves before, double-faulted to set up match point for Dellacqua, who had a year-end No. 78 ranking and had earlier knocked off No. 15 Patty Schnyder. The Australian then finished off a 3-6, 6-4, 6-4 victory with a forehand winner as the crowd erupted in cheers for the last local hope in the women's draw.