Jim Furyk carded a historic 59 on day two of the BMW Championship in Illinois.
The eight-time Ryder Cup player holed out nervelessly from inside three feet at his last hole, the ninth, to crown a round featuring 11 birdies, an eagle and a bogey.
The 12-under-par card at Conway Farms lifted Furyk, 43, level with Brandt Snedeker for the tournament lead and represented only the sixth sub-60 round on the PGA Tour.
Rory McIlroy had another round to forget carding a six-over 77 to sit in last position, 24 shots off the lead.
Graeme McDowell is one over par after posting a two-over 73.