Roger Federer and Novak Djokovic were untroubled, but Grigor Dimitrov was among five seeds to fall while Ash Barty and Serena Williams moved through as Naomi Osaka and Coco Gauff set up a third-round showdown at the Australian Open on Wednesday.
Federer produced an excellent performance in a straight-sets thrashing of Filip Krajinovic on Rod Laver Arena.
The Swiss great had received good news before even going on court after three seeds fell in his quarter of the draw, with Fabio Fognini only narrowly avoiding that fate.
Earlier, Djokovic dropped just seven games on his way to a thrashing of Tatsuma Ito in Melbourne.
Home favourite and world number one Barty was untroubled while Williams was below her best but still advanced during the night session as her bid for a record-equalling 24th grand slam title continued.
There is also the prospect of a mouthwatering showdown between two of the game's leading lights on Friday.
FEDERER, DJOKOVIC EASE THROUGH
Having lost a set in the opening-round victory over Jan-Lennard Struff, Djokovic suffered no such setback against Ito, winning 6-1 6-4 6-2.
A record seven-time champion in Melbourne and 16-time grand slam winner, Djokovic brushed past Ito on the back of 31 winners.
Federer was even more impressive later in the day, crushing Djokovic's Serbian compatriot Krajinovic 6-1 6-4 6-1.
The 20-time grand slam champion looked in fabulous form with 42 winners and just 14 unforced errors, reaching the third round in Melbourne for the 21st straight year.
Federer will next face John Millman, who upset 31st seed Hubert Hurkacz 6-4 7-5 6-3. The Australian stunned Federer at the US Open in 2018.
DIMITROV AMONG SEEDS TO CRASH OUT
Dimitrov, a semi-finalist in 2017, bowed out in a surprise 6-4 7-6 (8-6) 3-6 6-7 (3-7) 7-6 (10-3) loss to Tommy Paul.
The Bulgarian 18th seed went up by a break twice in the final set, but lost seven consecutive points from 3-3 in the match tie-break.
Matteo Berrettini, the eighth seed who reached the US Open semi-finals, was edged out by Tennys Sandgren 7-6 (9-7) 6-4 4-6 2-6 7-5.
Sandgren reached the quarter-finals in 2018 and will face Sam Querrey in an all-American third-round clash.
British 30th seed Dan Evans also made a second-round exit, losing to Djokovic's next opponent, Yoshihito Nishioka, 6-4 6-3 6-4.
CILIC, RAONIC ADVANCE AS TSITSIPAS GETS FREE PASS
Marin Cilic, runner-up in 2018, eliminated 21st seed Benoit Paire in a thriller.
The Croatian needed three hours, 33 minutes to overcome Paire 6-2 6-7 (6-8) 3-6 6-1 7-6 (10-3).
Next up for Cilic is a man he has lost to twice at the Australian Open in Roberto Bautista Agut, the Spanish ninth seed too good for Michael Mmoh 5-7 6-2 6-4 6-1.
Milos Raonic has reached at least the Australian Open quarter-finals four times and the Canadian has shown impressive form early on this year.
The 29-year-old served 19 aces in a 6-3 6-4 6-2 victory over Cristian Garin on Wednesday and next faces 2019 semi-finalist Stefanos Tsitsipas.
Tsitsipas advanced without hitting a ball after Philipp Kohlschreiber withdrew due to a muscle strain.
FOGNINI TAKEN THE DISTANCE BY THOMPSON
It is proving to be an arduous campaign for Fognini, who surrendered a two-set lead before holding his nerve in a decisive tie-break with home hope Jordan Thompson.
The Italian was taken the distance in his first-round meeting with Reilly Opelka after losing the first two sets, and this time it was the 12th seed who almost choked on a healthy lead.
Fognini hurt himself when punching his racket in frustration and was called for a foot-fault in the fifth-set breaker, but he got the job done in a memorable 7-6 (7-4) 6-1 3-6 4-6 7-6 (10-4) triumph that took more than four hours to complete.
Read: Australian Open: Nadal outclasses Dellien in first round
BARTY, SERENA UNTROUBLED
Barty brushed past Slovenian Polona Hercog 6-1 6-4 in just 66 minutes on the back of a consistent performance.
The Australian mixed 16 winners – nine of those from the forehand side – with 16 unforced errors, setting up a clash with Kazakh 29th seed Elena Rybakina.
Williams was left frustrated during the second set of her 6-2 6-3 victory over Tamara Zidansek.
The American star was pushed before advancing in one hour, 18 minutes, having committed 28 unforced errors, including 17 in the second set.
Next up for Williams is Wang Qiang, the Chinese 27th seed having rushed past Fiona Ferro 6-1 6-2.
OSAKA, GAUFF SET UP BLOCKBUSTER CLASH
Osaka's title defence stayed alive with a 6-2 6-4 victory over China's Zheng Saisai.
The Japanese third seed faces her biggest test yet in the third round, where Gauff awaits after the teenager's comeback win.
Gauff looked set for an exit, trailing Sorana Cirstea 3-0 in the final set.
But the 15-year-old fought back to claim a 4-6 6-3 7-5 victory and reach the third round at a grand slam for the third straight time.
Osaka crushed Gauff 6-3 6-0 when the pair met at last year's US Open.
WOZNIACKI STAYS ALIVE AS KVITOVA, KEYS ADVANCE
Caroline Wozniacki stretched her professional career for at least another match by beating Ukrainian 23rd seed Dayana Yastremska 7-5 7-5.
The 2018 Australian Open champion, who is retiring at the end of the tournament, came from 5-1 down in the first set and 3-0 behind in the second.
Last year's runner-up, Petra Kvitova, was tested in a 7-5 7-5 victory over Spain's Paula Badosa while Madison Keys also had moments of concern in her 7-6 (7-3) 6-2 win over Arantxa Rus.
Petra Martic (13) and Aryna Sabalenka (11) were among the seeds to fall, with the latter beaten by Carla Suarez Navarro in their opening-round clash.