Jason Day carded an eight-under-par 63 in round two of the BMW Championship as the Australian continues to sizzle in Illinois.
Seven birdies and an eagle at the last saw Day - who shot an opening-round 61 - move to 18-under for the tournament, five strokes clear of Daniel Berger and Brendon Todd.
The American pair can feel unlucky to be trailing by such a deficit after both shot an impressive 129 over 36 holes, but the 27-year-old, who clinched a first Major by winning the PGA Championship in August, finds himself in red-hot form.
Two-time Major winner Jordan Spieth, whom Day beat at Whistling Straits, is seven shots off the pace, along with Kevin Na.
Further back, Justin Thomas, George McNeill and Scott Piercy finished round two on 10-under.
