Serena Williams marked her return after a year out injured with a 1-6 6-3 6-4 win over Tsvetana Pironkova at the Aegon International in Eastbourne.
The reigning Wimbledon champion lost the first five games as the first set slipped past in less than half an hour but she rallied to win the second.
A break to start the third set nudged her ahead and she did not let it slip.
It was Williams' first match since winning Wimbledon last year and then suffering a serious injury to her foot.
The problem went on to cause life-threatening blood clots so she will have come into the Eastbourne tournament hoping for some morale-boosting results to get back in the swing of competitive tennis - but she could hardly have produced a worse first set.
The 29-year-old won just two points on her first serve in the whole set and produced numerous unforced errors, as her Bulgarian opponent easily moved ahead in the match.
Fortunately for the American, the second set produced a fresh start, and although her play was by no means fluent, it was effective as her first break of serve of the match helped her open up a 3-0 lead over the world number 26.
A weak Williams return into the net spared Pironkova a double break, but having finally got her eye in, the American began to gain the upper hand in the match.
Williams produced the first love game of the contest to go 5-2 up, with a superb angled forehand return from the back corner reminding everyone of how good she can be when she is at the top of her game.
Pironkova took the next, sealing it with a fine smash, allowing Williams the chance to serve for the set, and after dropping the first two points she rattled off four in a row to win the game and the set.
Having grabbed a lifeline back into the match after such a poor start to the match, it was never likely that Williams would pass up her second chance.
She broke her opponent in the opening game of the third set to gain the early initiative, although Pironkova broke back when Williams' double-handed forehand from the baseline clipped the top of the net and bounced down the wrong side, prompting a howl of frustration from the American.
Another shout, this time of delight, came at the end of the next game as Williams broke back to open up a 3-2 lead.
In her next service game, Pironkova held to love for the first time, to stay in touch at 4-3 down, only for Williams to take the next and move within one game of victory.
The Bulgarian refused to roll over and lose, pushing the game towards the two hour mark as Williams had her first opportunity to serve for the match.
And she wasted no time, winning her first match point to secure a victory which had looked extremely unlikely at the start of the tie.
"I'm a little rusty, but I really enjoy playing here and being back on grass," said the American afterwards.
"I'm just taking it one day at time, I hope you guys enjoyed the match and come back out and give me a little cheer, because I really need it and I'm so happy to be back."
Another former world number one in action on Tuesday was Ana Ivanovic.
She only managed a first serve percentage of 46% in her match against Germany's Julia Goerges, but secured a 6-4 6-3 victory.
And newly crowned French Open champion Li Na also secured her place in the second round with a 7-5 6-4 win over qualifier Tamira Paszek.
In the men's tournament, top see Jo-Wilfried Tsonga eased past Uzbekistan's Denis Istomin 6-2 7-5.