Novak Djokovic and Stan Wawrinka sailed through injury tests at the Australian Open on Tuesday with focused former champion Maria Sharapova also successfully getting back to business after her drug ban.
Twelve-time Grand Slam winner Djokovic has been out of action for six months with an elbow injury, but you wouldn't have known it in his 6-1, 6-2, 6-4 demolition of American Donald Young.
Former Melbourne champion Wawrinka also returned from half a year on the sidelines after knee surgery, having only decided he was fit to play at the weekend.
With the temperatures heating up, he was pushed to four sets by Ricardas Berankisbefore prevailing 6-3, 6-4, 2-6, 7-6 (7/2) in a tough workout he said was "proud" to come through.
Djokovic, gunning for a seventh Australian Open title, was also glad to be back, having missed the competitive edge.
"I wanted to start with the right intensity, which I have," he told the cheering crowd afterwards.
"I played perfect tennis in the first couple of sets and Donald came back in the third set."
World number one Simona Halep booked her place in round two, avoiding the first round exit that befell her in the past two years. But she made a meal of it against local hope Destanee Aiava.
Both the Romanian and her 17-year-old wildcard opponent needed on-court medical attention before the top seed ran out a battling 7-6 (7/5), 6-1 winner.
Sharapova, still working her way back from a 15-month ban for taking the performance-enhancing substance meldonium in Australia in 2016, showed glimpses of the tennis that made her a five-time major winner.
The 2008 Melbourne Park champion, now ranked 48, beat Germany's Tatjana Maria 6-1, 6-4 in her first Melbourne match in two years.
"I cherish these moments. I love it here," said the Russian, who returned from her drugs ban in April last year.
"It's been a couple of years and I wanted it to be really meaningful to me."
Fellow former world number one Angelique Kerber, who won the tournament in 2016, was also impressive in dismissing Anna-Lena Friedsam 6-0, 6-4.
"2017, I have said goodbye already, I am not looking back," she said after a forgettable last season that saw her relinquish the number one spot and slide down the rankings.
She is now on a 10-match win streak after a perfect early season.
Sixth seed Karolina Pliskova and eighth seed Caroline Garcia also progressed, in contrast to the other side of the draw that saw Venus Williams, Sloane Stephens and Coco Vandeweghe crash out on Monday.
American woes continued with Madison Brengle sent packing by British ninth seed Johanna Konta.
Young gun Alexander Zverev, seeded four, and Belgian seventh seed David Goffin were among men to make the second round.
But Canada's Milos Raonic, who has made at least the last eight over the past three years in Melbourne, was bundled out by 86th-ranked Slovakian Lukas Lacko in four sets.
It was his earliest Grand Slam exit in seven years as he fights back from a wrist injury.
Roger Federer, rated as favourite to win his 20th Grand Slam title even at the venerable age of 36, makes his entrance in a night match on Rod Laver Arena.
The second seeded Swiss, who is coming off an extraordinary 2017, when he won a fifth Australian Open title and a record eighth at Wimbledon, faces Slovenia's Aljaz Bedene.
Third seeded Garbine Muguruza also makes her bow in an evening match.
Former world number one Pliskova was among those to move smoothly into the second round, with a steady 6-3, 6-4 win over Veronica Cepede Royg.
"I'll take it match by match and I think I have a good chance," said the tall tattooed Czech, who made the quarter-final in Australia last year.
Sydney-born Konta also made the last eight in 2017 and showed no signs of her recent hip injury as she dismantled Brengle 6-3, 6-1.