Birdies at the first, third and fifth holes gave Northern Ireland's Michael Hoey the early lead in the Omega European Masters at Crans-sur-Sierre in Switzerland.
The event features three of the Official World Golf Ranking's top ten in Lee Westwood, Martin Kaymer and Rory McIlroy, returning to action after injuring his arm at the US PGA Championship three weeks ago.
Westwood was among the later starters, but McIlroy had to wait until only his third hole - the 410 yard tenth - for his first birdie and Kaymer was one under par as well after a two on the short 11th.
Former British Amateur Champion Hoey, who had the second European Tour win of his career in Madeira in May, led by one from Scot George Murray, last man into the tournament off his ranking, and Spain's Alejandro Cañizares.
Defending champion Miguel Angel Jiménez was another on one under, but Dane Thomas Björn, winner at Gleneagles on Sunday after a marathon five-man five-hole play-off, bogeyed the 11th and 13th.
Hoey went to four under on the long ninth, but bogeying the 11th cost him the lead.
That was because Kaymer, recapturing the form which swept him to World Number One earlier in the year, turned in a three under 32 and then birdied the par five first, while New Zealander Mark Brown grabbed birdies at four of the first seven holes.
The pair were a stroke ahead of Hoey, Murray and Canizares, with McIlroy and Jiménez staying well in touch at two under after further birdies at the 15th and 16th respectively.
Björn, meanwhile, returned to level par by picking up strokes at the 14th and 15th, the two par fives on the back nine.
