Ochoa and Sorenstam, ranked first and third respectively on the LPGA Tour's money list, are two of the leading candidates for Player of the Year. Ochoa, with four wins and Sorenstam, a three-time winner, including the U.S. Women's Open, both rank in the top 5 in the points race for that coveted title.
Seon-Hwa Lee, who has already clinched the LPGA Tour Rookie of the Year title, and Sophie Gustafson, the 2003 champion, are knotted in third place at 4-under-par 68.
Paula Creamer and Stacy Prammanasudh share fifth place at 2-under-par 70.
Michelle Wie, who turned 17 this week, had an interesting round on Thursday, one year after her professional debut. This time last year, Wie appeared to finish fifth, but was disqualified for signing an incorrect scorecard after a reporter noticed she took an improper drop on Saturday and never penalized herself.
On Thursday, Wie carded a tough 2-over 74 and is part of a group tied for 12th place.
Wie was 1 under through the turn, then ran into some trouble at the 11th. She double-bogeyed No. 11 to move to plus-1, but Wie came back with a 45-foot eagle putt from the fringe at the par-5 12th.
She parred 13, but once again, her driver let her down on the par-4 14th. Wie's tee ball landed against a rock and after several minutes for a ruling, Wie barely advanced her next shot. She took an unplayable lie, whiffed one and finally hit her sixth from short of the green. Wie badly missed a 12- footer for triple-bogey and converted a tricky 3-footer for quad.
The 17-year-old birdied 17 on the way in to salvage her round.
Ochoa, who last week won in her native Mexico, started nicely with two birdies in her first three holes, including a 7-footer at the third. She did not record another birdie on the front nine and made the turn at 2-under-par 34.
Ochoa birdied the 10th, then parred No. 11. At the 12th, Ochoa two-putted from close to 50 feet for a birdie, which got her to 4 under par and tied for the lead at the time.
At the par-3 13th, Ochoa hit a 5-iron to 6 feet to set up another birdie. After a long delay on the 14th tee box, Ochoa found the fairway, knocked her second to 4 feet and rolled in her third consecutive birdie putt. She was 6 under par, but that was short-lived as she bogeyed the par-5 15th.
She parred out to stay in a tie for the lead.
Sorenstam, the two-time defending champion and a five-time winner of this event, bogeyed the second, but got the stroke back with a birdie at the par-5 third.
The Swede broke into red figures with a 3-foot birdie putt at the seventh. At the par-3 eighth, Sorenstam drained a birdie putt from a similar length as the hole before and made the turn at minus-2.
Sorenstam ran home a long birdie putt at the 11th to get to 3 under par. She converted a 7-foot par save at 12 and birdied two in a row from the 14th.
For the first time in five years, Sorenstam is not a shoe-in to win Player of the Year honors, although a sixth title in this event would go a long way to closing the gap between herself and Ochoa.
The other contenders for Player of the Year are under par as well. Karrie Webb, second on the money list, and Cristie Kerr joined LPGA Champion Se Ri Pak in a tie for seventh at 1-under-par 71.
Women's British Open champion Sherri Steinhauer and U.S. Women's Open runner-up Pat Hurst are tied for 10th at even-par 72.