Ross Fisher of England and Stephen Gallacher of Scotland each shot a 6-under 65 to share the lead of the Portugal Masters after the opening round Thursday.
Fisher made birdies on three of his first six holes and then birdied four of the first five holes on his back nine.
''It's been coming for a while and it's nice to see the hard work paying off,'' Fisher said.
Gallacher shot a bogey-free round on the Oceanico Victoria Golf Course.
''There's not much rough, and the greens are unbelievably good,'' Gallacher said. ''I got off to a good start, which was nice, but when the wind picked up it was pretty tough.''
The co-leaders were followed by George Murray of Scotland on 5 under. Swedish pair Fredrik Andersson Hed and Christian Nilsson, Shane Lowry of Ireland, South Africa's Jbe Kruger and Jamie Donaldson of Wales were at 4 under.
Defending champion Tom Lewis shot a 69, as did Martin Kaymer, who holed the putt that kept the Ryder Cup with Europe less than two weeks ago.