Paul Waring turned in 29 to set the early pace as day one of the Nordea Masters got under way at Hills Golf Club.
The Englishman finished a career-best 60th on last season's Race to Dubai Rankings presented by Rolex but is currently 147th as he searches for that elusive first European Tour win.
Five birdies on the back nine in Gothenburg gave him an excellent start at five under, with Scotland's Scott Jamieson and Frenchman Clément Sordet a shot behind.
Waring made a birdie-birdie-birdie start and added further gains on the 15th and 18th to jump out in front.
Jamieson also started on the tenth and he recovered from a dropped shot on the 11th with birdies on the 12th, 14th, 15th, 16th and 18th in his first ten holes.
Sordet got off to a hot start with four consecutive birdies but then recorded five pars to turn in 32.
Another Frenchman in Matthieu Pavon, home favourite Christofer Blomstrand, Finnish pair Oliver Lindell and Tapio Pulkkanen, and Chilean Mark Tullo were then at three under.
