They played kids' tennis together in Belgium, shared hotel rooms as teenagers and respect each other on and off the court.
Tonight, Justine Henin-Hardenne and Kim Clijsters meet in the final, the third time in nine months the Belgians will play for a Grand Slam championship.
Clijsters is looking for a breakthrough, having lost to top-ranked Henin-Hardenne in the French Open and U.S. Open.
The Belgians advanced to the final with straight-set wins Thursday. Henin-Hardenne defeated Fabiola Zuluaga 6-2, 6-2 and Clijsters, still bothered by a bruised left ankle, beat Patty Schnyder 6-2, 7-6 (7-2).
"It's going to be another great moment in my career," Henin-Hardenne said. "And people are going to make a lot of noise, again _ it's an all-Belgian final, which I understand is huge for a little country."
Clijsters and Henin-Hardenne have played 17 matches as pros, including eight times in 2003, with Clijsters holding a 9-8 edge.
But the two that mattered most came last year, when Henin-Hardenne won the French Open 6-0, 6-4 and the U.S. Open 7-5, 6-1.
The progress of Henin-Hardenne and Clijsters has been amazingly similar at Melbourne Park, where both are in the final for the first time.
Neither has dropped a set in six matches. Henin-Hardenne won her first-round match 6-0, 6-0. One round later, Clijsters won 6-0, 6-0.
Henin-Hardenne has lost 31 of 75 games at the Open; Clijsters has lost 30-of-74. Henin-Hardenne spent 7 hours, 19 minutes total on court, 35 minutes more than Clijsters.
Both beat high seeds in the quarterfinals. Henin-Hardenne topped No. 5 Lindsay Davenport; Clijsters dispatched No. 6 Anastasia Myskina.
Despite their Grand Slam history, Clijsters does not believe Henin-Hardenne holds a psychological edge.
"I know what the problem was, and it wasn't mental," said Clijsters, who can take the No. 1 ranking with a win. I hope I have learned from those losses, so maybe third-time lucky."