Defending champion Thomas Pieters is by himself at the top of the Czech Masters leaderboard after shooting a 2-under 70 in Saturday's third round for a two-stroke lead.
The Belgian began the round sharing the lead with Jeff Winther of Denmark but moved ahead after three birdies at the front nine and another birdie on the 10th.
But Pieters fell back with two straight bogeys on the 11th and 12th for a 12-under 204 total at the Albatross Golf Resort near Prague.
Paul Peterson of the United States produced the best third round with an 8-under 64 to equal the course record. After a flawless round with eight birdies, Peterson surged to second with a 10-under 206.
Winther is a shot further back, tied for third with Englishman Robert Rock.