British number one Johanna Konta reached the second round in Birmingham with victory in her first match since her French Open semi-final defeat.
The 28-year-old seventh seed beat Estonia's Anett Kontaveit 6-4 6-2.
Compatriot Heather Watson was beaten by Czech Barbora Strycova, starting well before losing 3-6 6-3 6-4.
Fourth seed Elina Svitolina and fifth seed Aryna Sabalenka suffered shock defeats on the opening day at the Nature Valley Classic.
Meanwhile, in the doubles 22-year-old Briton Harriet Dart and her surprise partner, seven-time Grand Slam singles champion Venus Williams, lost in a match tie-break to Ukrainian Nadiia Kichenok and American Abigail Spears, going out 4-6 7-6 (7-3) 10-7.
- Andy Murray column: 'Meeting Royal surgeon proved pivotal'
- Live scores, schedule and results
- Alerts: Get tennis news sent to your phone
Konta wins on return to grass
Konta, who has risen to 18th in the world rankings from 45th at the start of April, skipped last week's Nottingham grass-court event but started here in confident style.
Following an impressive clay-court season, in which she reached two WTA finals before her run to the last four at Roland Garros earlier this month, she showed she was ready to back it up on grass.
With two weeks to go before the start of Wimbledon, Konta put in a convincing display in a tricky first-round draw against a player ranked just two places below her.
Her dominant serve was once again key, taking 81% of points on her first serve.
She broke in the fifth game of the opener before being pegged back for 4-4 but immediately broke back before serving out the set to love. Breaks in the first and seventh games of the second set up the victory with 73 minutes on the clock.
"I'm so happy to be back on home soil and to be in front of you guys again," she said. "I'm so pleased to get started on the grass, this is a such a privileged time for the Brits so I'm happy.
"I had a few days off, did not get too much practice on the grass because of the weather, then I got back into training."
Watson failed to join her in the next round, despite winning the first set and saving five match points in a spirited performance against Strycova, who is ranked 64 places above the British world number 115.
Svitolina and Sabalenka stunned in first round
The big upset of the day was the 6-3 3-6 6-4 defeat for world number seven Svitolina at the hands of Russian world number 62 Margarita Gasparyan.
The 24-year-old broke the Ukrainian's serve in the opening game on her way to taking the first set.
Svitolina, also 24, who won the WTA Finals event in 2018, secured an early break in the second set to level it.
But Gasparyan gained a 4-1 lead in the deciding set and held on for the victory.
The Russian, who has recently recovered from a career-threatening knee injury, said: "It was a tough time and I didn't know if I could play tennis any more but now I'm here in a big tournament so this is something special for me."
Gasparyan will play either compatriot Ekaterina Alexandrova or Petra Martic of Croatia in the last 16.
Belarusian world number 10 Sabalenka followed Svitolina out of the exit door with a 3-6 6-2 7-6 (7-1) defeat by Taiwanese world number 28 Hsieh Su-wei.
But third seed Karolina Pliskova progressed to the second round with a straightforward 6-3 6-4 win over Romania's Mihaela Buzarnescu.
The competition is being held at the Edgbaston Priory Club and also includes world number one Naomi Osaka and French Open champion Ashleigh Barty.
Dart savours doubles with 'incredible champion'
There were a few raised eyebrows when the doubles partnership of Dart and Williams was announced.
A 39-year-old American former world number one and a 22-year-old British world number 157 are an unlikely pair - never mind that Williams rarely plays doubles with anyone other than younger sister Serena.
Despite taking the first set against Kichenok and Spears, they were edged out to prevent Williams celebrating her birthday with a win.
But Dart, who like Williams is in singles action on Tuesday, still took a lot away from the experience.
"I was a little bit nervous but it was such an amazing experience and something I'll treasure for the rest of my life," she said.
"It's great to learn from someone like her. She's just an incredible champion."