Jason Dufner has ended day two of the Byron Nelson Championship in Texas with a one-shot lead at the top of the leaderboard.
The American added to his first-round score of 67 with a 66 to put him on seven-under-par.
Fellow countryman Chad Campbell is a shot further back with five others including overnight leader Ryan Palmer. Japan's Ryuji Imada has a share of third on five-under.
Ireland's Padraig Harrington is in contention going into the weekend as two birdies helped him finish Friday on three-under.
