Gary Ballance and Adil Rashid hit chanceless centuries as Yorkshire reached 332-5 on day one against Somerset at Headingley.
The fifth-wicket pair put on 207 after coming together with Yorkshire, who opted to bat, on 75-4.
Somerset seamer Peter Trego (2-67) had openers Adam Lyth and Joe Sayers both caught behind by wicketkeeper Jos Buttler in his opening spell, Lyth for a duck in the first over and Sayers for one off 25 balls.
Phil Jaques and Andrew Gale added 54 in good time for the third wicket but Gale (17) edged through to Buttler off Alfonso Thomas' bowling and Steve Kirby had Jaques held at slip by Marcus Trescothick for 49 to leave Yorkshire in trouble prior to lunch.
Somerset skipper Trescothick had dropped the same batsman on 22 off Trego's bowling.
The visitors had to wait until the final hour to make another breakthrough as Ballance and Rashid made hay in the sunshine, compiling a record stand for Yorkshire's fifth-wicket at the ground in first-class matches, overtaking the 196 by Roy Kilner and George Hirst against Gloucestershire in 1919.
It was also Yorkshire's highest for the fifth wicket against Somerset, beating the 157 put together by Jonathan Bairstow and Ballance at Taunton two years ago.
After the second new ball was taken, Zimbabwe-born left-hander Ballance went to his 14th first-class hundred from 187 balls before being trapped lbw by ex-Yorkshire paceman Kirby (2-85) for 107, including 13 fours.
Rashid advanced to three figures - in his case for the fifth time in his first-class career - in the company of Andrew Hodd (14no) and remained unbeaten on 120 at the close.