Glamorgan 176 for 3 (Allenby 96*) Somerset 169 for 4 (Trego 94, Wagg 3-44) by seven runs
Jim Allenby led from the front with the Glamorgan captain just missing out on a century as his side saw off Somerset by seven runs to win at Taunton.
Peter Trego nearly did enough to complete a successful chase of 177 in an entertaining game but Glamorgan held on for a fine win.
Jacques Rudolph and Allenby added 92 runs for the opening wicket before the former was caught off the bowling of Max Waller for 40. Chris Cooke and Darren Sammy, who made just 3, did not hang around too long to support Allenby, who continued to score quickly to keep the Glamorgan total ticking over.
Nine fours and three sixes saw Allenby end the innings unbeaten on 96, with Graham Wagg at the other end.
Wagg then took centre stage with the ball as he found his rhythm straight away to put the home side in command. Marcus Trescothick was caught behind in the first over having scored just four with Wagg also snaring fellow opener Craig Kieswetter, who only managed to score one run from six deliveries.
Trego had already started building an impressive score when Kieswetter fell and remained in fine fettle as he was joined at the crease by Alviro Petersen. The duo added 60 runs to the total before Petersen was caught off the bowling of Andrew Salter for 34.
James Hildreth proved just as capable as he supported Trego while playing his own aggressive game at the same time.
Trego hit 13 runs from the opening four deliveries of the final over to finish on 94 not out but Somerset ran out of time and, when Hildreth was caught off Wagg with the final ball of the match, it was Glamorgan who were left celebrating a third South Group success.