Venus Williams beat Slovakia's Daniela Hantuchova 6-4, 6-3 today to become the first player through to the semi-finals of the Australian Open today.
The world number two struggled to find any rhythm on her serve and also made 32 unforced errors but was still too powerful and experienced for seventh-seed Hantuchova.
One of her six aces was timed at 201 kilometres per hour, the fastest serve by any woman since 2001.
Hantuchova managed to break Williams's serve early in the first and second sets but conceded five breaks on her serve to go down in one hour and 15 minutes.
Williams will play Justine Henin-Hardenne in Thursday's semi-finals after the Belgian beat Virginia Ruano Pascual 6-2 6-2.
In the men's competition, three-time winner Andre Agassi beat French 12th seed Sebastien Grosjean 6-3, 6-2, 6-2 to advance to the men's semi-finals.
Second-seed Agassi will play fourth seed Juan Carlos Ferrero of Spain or unseeded South African Wayne Ferreira.