Ireland's Leona Maguire, Chevron Championship winner Lilia Vu and two-time major champion Brooke Henderson won their opening matches at the Bank of Hope LPGA Match-Play, but there were defeats for Britain's Gemma Dryburgh and Jodi Ewart Shadoff.
Maguire beat Linnea Strom 4&2, while top-seed Vu saw off Lauren Hartlage 4&3 and Henderson defeated Yaeeun Hong 3&2 on day one of the 64-player event in Las Vegas.
Maguire, back from a three-week break, said: "[It was] so nice to get back into the swing of things. I think this is one of the best golf courses we play all year. It's in such great shape. You really have to execute your shots.
"I drove the ball nicely. It wasn't the tidiest round but I holed a couple of nice putts when I needed to."
Vu and Henderson are the only members of the world's top 10 competing in Nevada, in an event which sees the players split into 16 groups of four for round-robin play before the knockout stages are contested at the weekend.
The last 16 will be played on Saturday morning followed by the quarter-finals in the afternoon, with the semi-finals and final on Sunday.
Scotland's Dryburgh was beaten two up by Stacy Lewis on Wednesday, while England's Ewart Shadoff lost by the same margin to Yu Liu after the Chinese player won the final three holes.
Other notable names to begin with defeats included 2017 Women's PGA champion Danielle Kang and last year's Chevron Championship winner Jennifer Kupcho, who were beaten by Muni He and Carolina Inglis respectively.
Celine Boutier, the No 3 seed, was taken to 18 holes and won when opponent Min Lee double-bogeyed, with that match one of 13 that went the distance among the 32 played.
Watch the knockout stages of the Bank of Hope LPGA Match-Play live on Sky Sports Golf this weekend. Coverage begins at 11pm on both Saturday and Sunday.