Carl Pettersson, who had never broken 70 before in the PGA Championship, birdied three of his first four holes to take a one-shot lead after the first round of the season's final major.
Pettersson is chasing his first major championship title but he already has one victory this year in South Carolina, taking the RBC Heritage in Hilton Head in April. He would like to make it two wins in the Palmetto State after shooting a six-under 66 at the Kiawah Island Golf Resort.
"There is a long way to go but I am thrilled with my start," Pettersson said on Thursday. "I haven't contended much in majors. I think I have two top 10s. But I would love to have a chance to see what happens."
Former US Open winner Rory McIlroy heads a group of four players that are one shot back. American Gary Woodland, Spain's Fernandez-Castano Gonzalo and Swede Alex Noren all shot five-under 67.
Australians Adam Scott, Aaron Baddeley and Geoff Ogilvy, Northern Ireland's Graeme McDowell, defending champion Keegan Bradley and his fellow American player Scott Piercy, Joost Luiten of the Netherlands and 1991 PGA Championship winner John Daly are all tied for sixth two shots back of the leader.
The 34-year-old Pettersson, of Gothenburg, hit 12 of 14 fairways Thursday and 15 of 18 greens in regulation.
"Getting off to a good start was the key to the round," he said. "The wind started blowing a bit on the back nine but I carried my solid play, hitting a lot of fairways, a lot of greens and making a few putts. It was a great day for me."
McIlroy, who is chasing his second major championship title, got his PGA Championship off to a solid start as well, rolling in five birdies in a bogey-free round.
He started on the back nine and began his day with a birdie on the 447-yard, par-four tenth hole. He also had birdies on holes 14, 16, two and six.
"It is a great way to start a tournament," he said. "I thought I had to take advantage of the conditions. I am very happy."
McIlroy has a shot at overtaking Luke Donald as the top ranked player in the world if he plays well this week. In order to do that, the young Northern Irishman needs to win and have Donald finish worse than a two-way tie for second place.
The conditions were ideal at Kiawah Island as there was just a light wind and plenty of sunshine in the morning after several days of rain leading up to the first round.
Weather forecasters were predicting rain in the morning but the early starters were met with hot and humid conditions with temperatures of around 90 degrees Fahrenheit (32 Celsius).
McIlroy said the blue skies were unlikely to last all week.
"I am expecting this to be the best day of the week," he said. "I am just happy I got off to a great start."
Tiger Woods also got off to a sound first round with a three-under 69. His round featured three bogeys and six birdies, including three-straight birdies at the turn.
"I played well today and anything in the 60s is going to be a good start in a major championship and I am right there," Woods said.
British Open champion Ernie Els shot an even-par 72 while American Phil Mickelson struggled with a 73. Englishman Donald shot a two-over 74.
One of the strongest fields ever put together for a tournament is tackling this week the Ocean Course, which at 7,676 yards (meters) is the longest course in major championship history.
A total of 102 of the 103 top ranked players in the world are competing this week at Kiawah Island.