R1 LEADERBOARD -5 T Woods (US) -2 P Mickelson (US) +1 M Campbell (NZ) +3 V Singh (Fij)

Woods, the Masters and Open champion, overcame a stomach virus and injured ankle to fire 67 in Kauai to lead Phil Mickelson, the USPGA champion.

New Zealand's Michael Campbell, the US Open winner, shot 73 with Fiji's Vijay Singh, the world number two, on 75.

"I just need to stay upright. I have been feeling kind of sick," said Woods.

Woods, the world number one, and fellow American Mickelson shared the lead with three holes to play.

But left-hander Mickelson, who scorched a 59 in the final round last year to win, made back-to-back bogeys.

Woods sank an eight-foot birdie putt at the last to seal the halfway lead in the 36-hole event.

"By the end I was feeling pretty good out there," said Woods, a 10-time major winner who triumphed in this event five straight times ending in 2002.

Mickelson said: "There's an old saying, 'Beware of the ailing golfer'. And whenever he's complaining, we know we're in trouble."

Campbell was making his debut in the tournament after being the first major winner from his homeland since Bob Charles won the 1963 Open.

"It's just a privilege to be here, really," he said. "I've been watching this in the last 14 years on TV and it's nice to be a part of it now. A part of history."

Singh's challenge faltered when he notched up a disastrous seven at the par-three 11th.