World number one Mark Selby was at his ruthless best as he built a 6-2 lead over qualifier Kyren Wilson in their World Championship quarter-final.
Wilson, who has beaten top-10 seeds Joe Perry and Mark Allen, lost the first three frames despite having chances.
Selby, the 2014 champion, made it 4-0 at the mid-session interval after a break of 101 and was 6-0 up before Wilson claimed the last two frames.
China's Ding Junhui also impressed as he built a 6-2 lead over Mark Williams.
Two-time Crucible champion Williams won the opening frame of their best-of-25 tie, but Ding compiled six half-centuries as he claimed six of the next seven to establish a commanding lead.
Ding, an 11-time ranking event winner, looked sharp and in good rhythm throughout, edging the safety exchanges and scoring heavily when given the opportunity.
Both matches resume on Tuesday at 19:00 BST and, with eight frames scheduled, both could feasibly play to a finish a session early.
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Six-time champion Steve Davis: "Having had the experience of going all the way here, Selby knows how to pace himself. Mentally, it's knowing you're in the quarter-finals, you've had a hard week, but you're still nowhere in the event. The quarter-final is arguably where it all starts."
Former champion Ken Doherty: "To win those last two frames showed Wilson's character and keeps him in this match. He's had two great wins and now he's got to come back this evening and do it all again. Winning those last two frames will certainly give him a bit of a gee up.
"Ding has been bereft of confidence for the last 12 months and slipped under the radar, but maybe it's done him good. He's come into these championships under the radar, nobody expecting anything of him. He's not at his best but he's in the quarter-finals and looking good at the moment."