Sjoholm, looking for his first tournament win as a professional, had four birdies on each side of the Royal Park I Roberi course in building a one-stroke lead over Lee Slattery.
Slattery closed with back-to-back birdies for a 65. Seven golfers, including Keith Horner -- who overcame a double bogey and a bogey on the day -- are tied for third at 6-under 66. A total of 99 players were at least 1-under in the first round.
Sjoholm is coming off consecutive tournaments in which he missed the cut by one stroke. On the scorecard his round looked tame with eight birdies and 10 pars but on the course is was more of an adventure.
"I hit it basically everywhere," Sjoholm said. "I was in the woods a lot and made some funny birdies today. It was a big, fighting 64 rather than a solid 64 but it's great fun to be 8-under."
Sjoholm drove into the trees at the third hole but ended with a par by dropping in a putt from the fringe. He also reached the trees in 13 and used a 20-foot putt to save par.