Erin - England's Paul Casey looked to reel in Rickie Fowler at the top of the US Open leaderboard here Friday as the second round got under way.
Fowler surged into a one-shot lead on Thursday with a brilliant opening seven-under-par 65 in his quest for a first major at the Erin Hills Course in Wisconsin.
Benign conditions on Thursday made for a feast of low-scoring, with a record 44 players dipping under par - the most ever in the first round of the US Open.
Play started on Friday in similarly calm conditions, with only gentle breezes blowing across the sprawling 7,441-yard par-72 layout.
Fowler will tee off Friday in the afternoon session alongside Japan's Hideki Matsuyama and Spaniard Jon Rahm.
Casey, who finished on six under on Thursday after an opening 66, teed off early and was looking to move into the lead before Fowler gets on the course.
The world number 14, teeing off on the 10th hole, made a solid start, opening with a par.
He then joined Fowler on seven under with a birdie on the par-four 11th, playing a brilliant iron from the fairway to three feet to tap in.
But Casey's momentum ran into the buffers on the next hole, when he twice found the thick rough and had to settle for a bogey five to drop back to six under.
The 39-year-old then parred the 13th to remain one shot off the lead alongside Xander Schauffele, the lowly ranked American who was also out on the course early Friday.
Schauffele, ranked 352nd in the world, launched his second round with a par after an opening 66 on Thursday.
Elsewhere on Friday, the world's top three players - Dustin Johnson, Rory McIlroy and Jason Day - will attempt to resurrect their chances after disappointing first round displays.
Defending champion Johnson will aim to bounce back from a lacklustre three-over-par 75 when he tees off alongside Jordan Spieth and Martin Kaymer in the afternoon session.
McIlroy meanwhile has a bigger hole to climb out of after a six-over-par 78 on Thursday.
The world number two from Northern Ireland looked set for another roller coaster round on Friday after a fluctuating start.
A bogey on the par-four 12th was followed by a birdie on the 13th to leave him at six over through four holes.
Australian world number three Day meanwhile - who shot a seven-over-par 79 on Thursday - opened his second round with two birdies and a bogey in his first three holes.