Chris Dent hit the highest score of the Yorkshire Bank 40 season to power Gloucestershire to a seven-run win over Group C rivals Glamorgan.
Dent, whose previous top score in List A cricket was 36, finished 151 not out after hitting 17 boundaries and three sixes in a 113-ball knock.
His innings helped the visitors to 288 for five at the SWALEC Stadium and it proved enough for victory although the hosts made a valiant chase.
In reply, Glamorgan got off to the worst possible start as they lost William Bragg for a duck after he was trapped leg before by James Fuller.
But fellow opener Mark Wallace did his best to give the hosts victory after carrying his bat for 118 not out.
He received good support from Jim Allenby (39), Murray Goodwin (36) and Graham Wagg (54 from 43 balls) but, needing 17 from the final over, he couldn't pull off an unlikely victory despite hitting the third ball for four.
Fuller finished with three for 42 for Gloucestershire.
Both teams now have two wins from their opening four games, Glamorgan still in second place but Gloucestershire up to third.