Ross Fisher of England and Stephen Gallacher of Scotland both shot 6-under 65s to share the lead of the Portugal Masters after the opening round on Thursday.
Fisher made birdies on three of his first six holes and then birdied four of the first five holes on his back nine. He also bogeyed No. 16.
Gallacher shot a bogey-free round.
The co-leaders were followed by George Murray of Scotland on 5 under.
Martin Kaymer, who holed the putt that kept the Ryder Cup with Europe less than two weeks ago, shot a 69 on the Oceanico Victoria Golf Course.
Ryder Cup teammate Francisco Molinari finished level par, while Europe captain Jose Maria Olazabal was 4 over.