Twenty20 Cup semi-final, Trent Bridge: Surrey 147-9 (20 overs) beat Gloucestershire 142-6 (20 overs) by five runs
Azhar Mahmood helped Surrey into the final thanks to a brilliant bowling display against Gloucestershire.
The all-rounder picked up the crucial wickets of Jonty Rhodes, Ian Harvey and Alex Gidman as the Gladiators fell five runs short of Surrey's total of 147.
A fine innings of 61 from Gidman had brought Gloucestershire back into contention after losing early wickets.
But accurate bowling at the death from Mahmood and captain Adam Hollioake helped the Lions to a tight victory.
Hollioake had won the toss and decided to bat and his side made a typically explosive start with Ali Brown, who made 18 from seven balls including two sixes and a four, before he skied a catch to Matt Windows in the deep.
Opener Ian Ward was the only Surrey batsman to make a real impression, but he fell one short of his half century when he was bowled by Ian Harvey, who picked up two wickets.
Mark Hardinges and Martyn Ball were also in the wickets, with Hardinges picking up 3-37, while Ball finished with 2-26.
But the Gladiators got their innings off to the worst possible start when stand-in captain Craig Spearman was bowled by James Ormond for one in the first over.
And they soon in deeper trouble when Azhar removed danger men Rhodes for a duck and Harvey for seven soon after.
A partnership of 52 between Gidman and Hardinges helped the Gladiators build a platform to chase Surrey's total.
Hardinges was bowled by Hollioake for 24, but Gidman kept up the pressure, reaching his half century in style with a huge six off Ian Salisbury.
But the Gladiators chances of victory began to fade when Azhar bowled Gidman for 61.
And despite the best efforts of Chris Taylor (20 off 15 runs), the Gladiators could not find the 17 runs they needed for victory in the last over.
Azhar finished with figures of 3-28, with James Ormond, Saqlain Mushtaq and Hollioake picking up a wicket apiece.
Gloucestershire: C M Spearman (Capt), I J Harvey, J N Rhodes, M A Hardinges, C G Taylor, A P R Gidman, M G N Windows, M C J Ball, S P Pope (Wkt), J Lewis, A M Smith
Surrey: I J Ward, A D Brown, R Clarke, A J Hollioake (Capt), G P Thorpe, M R Ramprakash, Azhar Mahmood, J N Batty (Wkt), Saqlain Mushtaq, I D K Salisbury, J Ormond