Tiger Woods and Padraig Harrington started the US PGA Championship at Hazeltine National as they finished the World Golf Championships-Bridgestone Invitational, locked in a duel at the top of the leaderboard.
Woods opened his account in the final Major of the year with a bogey free, five under par 67, while defending US PGA champion Harrington shot a 68 to throw down the gauntlet to an afternoon wave of starters that included world number two Phil Mickelson, and 2009 Major winners Angel Cabrera, Stewart Cink and Lucas Glover.
"I was just very comfortable with what I was doing today," Woods said after playing the par 72, 7,674 yard Hazeltine, the longest course in Major Championship history.
"The golf course is set up very fair. It's difficult but as Paddy (Harrington) and I were saying, you don't (usually) see pins, six, seven, eight feet from the side. It's normally three and four. So you can make birdies and be a little more aggressive going at these flags. You don't have to be as conservative."
Having gone toe to toe at Firestone Country Club last Sunday in the final round, Woods and Harrington were paired once more for the first two rounds alongside Rich Beem, the 2002 champion when the event last visited Hazeltine.
A triple bogey from Harrington last Sunday had decided their battle and handed Woods his fifth victory of the year and the World Number One, a four time US PGA champion, began the quest for his 15th Major looking for a third tournament win in as many weeks.
The pair matched each other hole for hole initially, both sinking birdies at their third hole of the day, the 12th, the Irishman thanks to a great approach shot to six feet and Woods with a 25 foot putt.
Woods stole a march on the 642 yard, par five 15th, getting up and down from a bunker but at the next hole Harrington caught up thanks to another good iron shot to six feet.
Harrington had his only stutter of the day when he bogeyed the first but bounced straight back with a birdie at the next hole to return to two under.
Woods also birdied the second hole and got to four under with a birdie at the par five third, his 12th, Harrington joining him there thanks to another good iron shot at the sixth, from where he made a birdie three.
Woods added another birdie from three feet at the seventh, his 16th, to go into the outright lead at five under, finally separating himself from the Irishman to take the clubhouse lead in 67.
"I'm very happy," Harrington said. "First day of a Major it's always good to keep yourself in there.
"I think I did a little bit more than that; any time you break 70 you've got to be pleased. It's a little bit tough when you're coming back to defend the tournament, there's a little bit more spotlight and focus, so shooting 68 is a good start."
Beem, the third man in the group and US PGA champion at Hazeltine seven years ago, posted a 71.
American Hunter Mahan closed with a bogey five at the ninth for a three under 69 alongside Australia's Robert Allenby and Mathew Goggin and big-hitting Alvaro Quiros of Spain, while Vijay Singh and David Toms joined them in a tie for third place from the afternoon side of the draw.
In-form World Number 13 Lee Westwood, who tied for third place at last month's Open Championship, sent down two birdies in his last five holes for a two under 70, a score matched by Northern Ireland's Graeme McDowell and fellow Europeans Søren Kjeldsen of Denmark and Gonzalo Fernandez-Castaño of Spain.
Northern Ireland's Rory McIlroy, on his US PGA debut, shot a one under 71, as did Spain's Sergio Garcia and England's Luke Donald.
World Number Three Paul Casey withdrew early this morning due to a rib injury, his place in the 156 man field taken by American Tim Petrovic, while former champion John Daly shot a 76 and then withdrew, citing a back injury.
England's Ian Poulter closed with bogeys at the 17th and 18th for a level par 72, while Scotland's Alastair Forsyth, Ross Fisher and Justin Rose of England and Germany's Martin Kaymer all shot 73s.
Asked for his assessment of his round Poulter replied: "Do you really want to know? I'm disappointed. Two bogeys to finish is not good enough...it's a shame."
US Open Championship winner Glover was the best of the 2009 Major winners, playing together in a traditional US PGA group. Glover posted a 71 with Open Championship winner Cink recovering from five over after five holes to a one over 73 while Masters Tournament winner Cabrera carded a 76.