Chris Taylor and Craig Spearman inspired Gloucestershire to a 27-run victory over Somerset at Bristol and a place in the Twenty20 Cup quarter-finals and end the holders' reign.
Taylor hit a competition-best 83 and Spearman 63 as the home side created a stadium record Twenty20 score of 227-4 after winning the toss.
Mark Hardinges (33) and Alex Gidman (39) also made brisk contributions.
Somerset made a spirited attempt to reach their target, but the were bowled out for 200 to bow out of the competition.
Justin Langer hit 49 and Peter Trego 47 before a flurry of late wickets, three of them run-outs.
Gloucestershire have now won five group matches on the trot after an opening-game drubbing by Somerset and exacted revenge - even without Ian Harvey, who was sidelined by a bruised thumb.
Spearman and Hardinges gave them a great start with a stand of 89 off nine overs.
Spearman's hit three sixes and eight fours in his 32-ball innings. But it was man-of-the-match Taylor who did most to put the game beyond Somerset, blasting four sixes and nine fours in sparkling 34-ball contribution.
Gidman ensured there was no respite for the Somerset bowlers.
Richard Johnson went for 49 off his four overs, Peter Trego 36 from three and Gareth Andrew 42 from three.
Despite short boundaries, the total always looked likely to be beyond Somerset, but they stayed in with a chance thanks to Australia opener Langer - who hit six fours and a six - and Trego, whose 32-ball innings featured two sixes and four fours.
It was the Gloucestershire spinners who claimed both batsmen.
Langer was caught off Martyn Ball and Trego fell to another skyer off Ian Fisher.
With the pressure of scoring at 12 an over, Somerset's middle order folded to some sharp Gloucestershire fielding.
James Hildreth and Andrew were run out, while the home side also held their catches.
The one moment of controversy in the match came when Somerset captain Cameron White was run out for nought backing-up by Craig Spearman after being sent back by Langer.
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