Sophia Popov holds a three-shot lead in the individual contest at the Aramco Team Series event in New York, as Team Strom hold the advantage in the team event.
The former AIG Women's Open champion carded seven birdies in a bogey-free 65 at Glen Oaks Club to build a strong advantage over a six-strong group tied for second, with Solheim Cup team-mate Anna Nordqvist and England's Bronte Law among those on four under.
Danielle Kang, Slovenia's Pia Babnik, South Africa's Lee-Anne Pace and France's Pauline Roussin Bouchard complete the group posting opening-round 68s, with world No 1 Nelly Korda and Charley Hull a further shot back after both starting the 54-hole event with a three-under 69.
"It has honestly been really good for me this week to focus on something different," Popov said. "I love team events, the Solheim Cup was huge for me, I had so much fun, and this is very much like it.
"You're playing as a team; it doesn't matter if you make one or two bogeys if you come back and make two birdies we are doing well as a team. I'm all in as far as the team goes, individually it's great if I'm playing well that's nice but that has mentally freed me up and made me enjoy it a little bit more."
Scotland's Michele Thomson and Becky Morgan of Wales both had steady outings to finish the day on two under, joining American stars Lexi Thompson and Jessica Korda five off the pace, while last year's Order of Merit winner Emily Kristine Pedersen opened with a first-round 71.
As well as the individual competition, the players' scores were also being entered in a team event, with Swede Linnea Strom's quartet taking the early lead on 18 under.
Team Popov are in second on 16 under, with the German joined in her team by Argentina's Magdalena Simmermacher, who is 11th in the Race to Costa del Sol, and England's Hayley Davis.
Law's team sit in third, with Team Korda and Team Pace in tied-fourth. The team event sees three professionals and one amateur compete in the same quartet, with the best two scores on each hole taken forward for the team competition.
Watch the Aramco Team Series throughout the week live on Sky Sports. Live coverage continues Friday from 6pm on Sky Sports Golf and - for free - on the Sky Sports Golf YouTube channel.