R1 LEADERBOARD US unless stated otherwise -8 N Castrale -6 P Hurst, C Kerr -5 D Delasin, C Kim, Seon Hwa Lee (Kor) Selected others: -4 M Hjorth (Swe) -2 K Stupples (GB), K Webb (Aus) -1 A Sorenstam (Swe), M Wie Level L Davies (GB), C Matthew (GB) +1 K Davies (GB)

Castrale, who has failed to make the cut in her two major appearances, had eight birdies and leads by two shots from Pat Hurst and Cristie Kerr.

Karen Stupples was the only British player to break par after a 70.

Defending champion Annika Sorenstam and 16-year-old Michelle Wie, last year's runner-up, were locked together on 71.

Castrale, 26, has been plagued by injuries that she dates back to a car accident in her senior year at High School.

"it's really only in the past 18 months or so that I've been fully healthy," said the player who won twice on the US Futures Tour last year to gain her full LPGA card.

"I've been playing pretty well this season but I just didn't feel I was getting a whole lot out of my rounds. But I stayed patient and today was great."

Out-of-form Sorenstam, aiming to win this event for a fourth-straight year, is looking to equal Tiger Woods' record of 10 career majors.

However the Swede, who has only one victory this season, could only end up on one under after a mixed round which contained three birdies.

"It does rather sums up how things have been going this year," she said.

"I only hit 10 out of 14 fairways and so I'm going to work on my driver this afternoon. It feels good, but I've just got to take it onto the course."

Teenage sensation Michelle Wie, who last week just missed out on qualifying for the men's US Open, struggled on the greens but carded three birdies in the final four holes to stay in contention.

"I felt I played really well but just couldn't get anything going," she said. "But the last four holes felt back to normal. Hopefully I can shoot really low tomorrow."

Stupples had six birdies in her round but four bogeys stalled her progress.

"It's been the same story for most of the season," said the 2004 British Open Champion. "I need to rule out the mistakes."

Fellow Brits Laura Davies and Catriona Matthew are two shots adrift of Stupples on level par.