Robert Karlsson and Johan Edfors of Sweden and Maarten Lafeber of Netherlands led the Portugal Masters after shooting 64s in the first round Thursday.
Karlsson and Edfors had bogey free rounds, while Maarten had six birdies over his last nine holes to help atone for an earlier double bogey.
Alexander Noren of Sweden was one shot back in fourth, tied with Mikko Ilonen. The Finn was the only afternoon starter among the top five.
European Ryder Cup team member Edoardo Molinari, another late starter, shot a 4-under 68.
"The greens were uneven," the Italian said. "I had one stupid three-putt from 20 feet on the seventh green. But when that happens it important to think about the putts you have made rather than the ones you miss."
A week of heavy rain also has softened the 7,231-yard course, leaving it playing longer than usual.
"The fairways are quite soft and it is a big hitters' golf course," Karlsson said. "If you hit it long you can still get up in two at all of the par-5s, but the shorter players are having to lay up short. So it is suited to the big hitters."
The conditions also could produce very low scores.
"If the wind stays down, this is one of the courses you can shoot very low, especially now when the rough is down as well," Edfors said. "So without wind, the 59 is possible."
Lafeber had 11 birdies and would have had the outright lead if not for a double bogey after he found water by the 18th green, his ninth hole of the day.