Yorkshire 156 for 3 beat Worcestershire 155 for 9 by seven wickets
Andrew Gale set up the easiest of Yorkshire victories at New Road and left Worcestershire stranded at the foot of Group A after their fourth defeat in five Clydesdale Bank 40 games.
Steven Patterson took four for 28 in the Royals' laboured progress to 155 for 9 and Gale continued his good form in the competition as Yorkshire eased home by seven wickets with 21 balls to spare.
The Yorkshire captain made 56 and lifted his aggregate to 285 from five innings after sharing in successive half-century partnerships with fellow-left handers Gary Ballance and Adam Lyth.
Rotherham-born left-arm spinner Shaaiq Choudhry secured Worcestershire's first success when Ben Scott stumped Ballance for 27 and Moeen Ali's off-spin accounted for Gale with a tumbling catch at mid-wicket by Jack Shantry.
Yorkshire never had to rush and Lyth was able to bat within himself until he took an unnecessary risk in going for a second run which would have completed a half-century. He was comfortably beaten by Alexei Kervezee's return from deep square leg.
Worcestershire were hopelessly short of runs despite James Cameron's third successive CB40 half-century and an eye-catching innings by 17-year-old schoolboy Aneesh Kapil. Kapil, who later bowled five overs at a lively pace, joined Cameron in a stand of 88 in 20 overs, which was all that stood between the home side and total collapse.
Struggling at 30 for 4 after two wickets each for Yorkshire's new-ball pair, Patterson and Oliver Hannon-Dalby, they folded again as soon as Kapil departed, lbw for 44 when pushing forward to the fourth delivery in a second spell by Adil Rashid.
Kapil who played for Wolverhampton in the Birmingham League at the age of 13, was unfazed by registering a duck for his club team only 24 hours before he was called up for a competitive debut in the county side.
A flamboyant stroke-maker, he hit four of the dozen fours that Worcestershire mustered in the entire innings, and fortunately for Yorkshire, a glaring let-off, when Hannon-Dalby put down a simple opportunity at short third man, cost them only two runs.
Similarly a let-off for Cameron - Ballance spilling an awkward chance at mid-wicket - was quickly brushed over. One run later, the Zimbabwean-born left-hander fell for 51, driving to mid-off as Patterson struck twice in his second spell.
Along the way, Cameron hoisted Rashid for a straight six but managed only two fours as Yorkshire, despite missing a contingent of first-teamers, took an unshakeable grip on what became a one-sided contest.