Richie Ramsay of Scotland and Edoardo Molinari of Italy each shot 8-under 62 to lead after the European Masters first round on Thursday.
Both carded bogey-free rounds in the thin Swiss Alps air to finish two strokes ahead of Englishmen Tommy Fleetwood and Graeme Storm, and Gareth Maybin of Northern Ireland.
Ryder Cup teammates Jamie Donaldson of Wales and Victor Dubuisson of France were in a group of seven players a further shot back on 5 under.
Thomas Bjorn of Denmark, the third member of Europe's team playing here who will face the United States in Scotland this month, was among 15 players shooting 4-under 66 on the 6,848-yard (5,486-meter) Severiano Ballesteros course.
Bjorn won two of the past three European Masters titles, and Ramsay was champion in 2012.