Seventy-five players were competing for 11 places over two rounds on the Old and New Courses at Walton Heath.
Raphael Jacquelin was next at 67. Jacquelin and Dyson played the New Course, which is considered easier than the Old and produced lower scores in the first round.
Dyson, who was tied for sixth at the 2007 PGA Championship, eagled the first hole and also had five birdies and one bogey.
I didnt have to make any long putts. I was hitting it close, he said. I kind of had it on a string.
Jacquelin says hes in a strong position.
The good thing is it means that after 5 under on the New, I can play the Old Course maybe more patiently, he said.
Jean-Francois Lucquin (68), Richard Bland (68), Brett Rumford (69), Christian Nilsson (69), Felipe Aguilar (69) and amateur Sam Hutsby (69) played the New Course. Simon Khans 68 was the best round on the Old Course. No one else broke 70.
The U.S. Open at Bethpage Black on Long Island begins June 18.