Na Yeon Choi shot 3-under 69 on Saturday to take the lead at the season-ending Group Titleholders.
The World No. 4 Choi entered Saturday in second place -- one shot behind Ai Miyazato -- before carding four birdies against one bogey to move to 12-under- par 204.
"I feel great right now and I have a lot of confidence and I'm ready to go," said Choi.
Miyazato, coming off a personal season-best 64, stumbled out of the gate on Saturday with a double-bogey on No. 2 and a bogey on No. 5 before tallying four birdies during her outward nine to finish with a 71. She is alone in second place at 11-under.
"After No. 9 I said to my caddie, it was really hard work the 18th holes but now I think I'm ready for that, I'm ready to play good," said Miyazato. "I think that conversation kind of helped."
First-round co-leader and Louise Suggs Rolex Rookie of the Year So Yeon Ryu is two shots back in third place after recording a 68, while Brittany Lincicome (70) and Karine Icher (70) are tied for fourth at minus-9.
The top-3 finishers in each official LPGA Tour event qualified for this event, which includes the top-31 players on the money list and the top-13 players in the world rankings.
World No. 2 Stacy Lewis, the only player to win four titles this season, is 2-under through 54 holes. She has already secured the 2012 Rolex Player of the Year award -- becoming the first American to receive the honor since Beth Daniel in 1994 -- but needs to win the $500,000 first-place check this week to have any chance of passing money list-leader and world No. 3 Inbee Park.
Park, who has secured more than $2.2 million in earnings, shot par on Saturday to stay at 4-under.
In addition to the money list, Park also holds a slight edge over Lewis in the race for the Vare Trophy, which is given for lowest scoring average. Park entered the tournament with an average of 70.20, while Lewis sat at 70.26
Defending champion Hee Young Park has carded 76-68-75 through the first three days to sit at plus-3.
World No. 1 Yani Tseng shot 69 on Saturday -- her best round of the weekend thus far -- to move to 1-over.
Michelle Wie resides near the bottom of the leaderboard at 13-over.
NOTES: Choi is seeking her second win of the season ... Last year, Hee Young Park collected her first LPGA Tour victory at the season-ending event. Park fired rounds of 71-69-69-70 to win by two strokes over Paula Creamer and Sandra Gal.