David Lingmerth shot a seven-under-par 65 to take a one-stroke lead into Saturday's session at the Memorial Tournament in Ohio.
The Swede managed seven birdies in a bogey-free round to boost his hopes of a first PGA Tour victory - and first professional win since 2012 - as he sits at the summit on 12 under.
Lingmerth is one shot clear of Jason Dufner, who holed two eagles for the second day in succession but a double-bogey on 12 ensured that the American is one off the pace heading into the weekend.
England's Andy Sullivan and Ryan Moore are two strokes back on 10 under, with overnight co-leader Hideki Matsuyama one behind on nine under following a second-round 71.
Matsuyama is one of six players currently tied for fourth, with one-time major winner Justin Rose among them.
Bo Van Pelt, whose eight-under-par 64 saw him share the lead with his Japanese counterpart after day one, fired a costly 72.
Shane Callaghan
