Novak Djokovic and Serena Williams won their matches at the Australian Open, but Petra Kvitova and Bianca Andreescu are out.
World number one Djokovic defeated American Frances Tiafoe in 4 sets in their second-round match in Melbourne.
The Serb came through 6-3, 6-7, 7-6, 6-3.
Also in the men's singles, third seed Dominic Thiem saw off Dominik Koepfer in straight sets.
There were wins for Milos Raonic and Diego Schwartzman, but Stan Wawrinka was beaten in five sets by Marton Fucsovics of Hungary.
Serena Williams breezed past Nina Stojanovic in straight sets, 6-3, 6-0, and remains on track for a record 24th Grand Slam title.
However, Serena's sister Venus Williams lost 6-1, 6 love to Sara Errani.
It was far from plain sailing for the world number two Simona Halep, who battled back from 5 games to 2 down in the third set to defeat Ajla Tomljanovic 7-5 in the deciding set of their encounter.
Petra Kvitova and Bianca Andreescu were knocked out.
Kvitova, a finalist two years ago, went down 6-4, 1-6, 6-1 to Sorana Cirstea of Romania.
2019 US Open winner Andreescu lost in straight sets to Hsieh Su-wei.
Naomi Osaka had no such worries, defeating Caroline Garcia 6-3, 6-3.
