Ian Saxelby took four for 16 as Gloucestershire defeated Northamptonshire by eight runs to register their first win in the Friends Life t20 and keep their opponents waiting for their opening success of the group campaign.
Kane Williamson (39) and Ian Cockbain (36) were the main contributors to Gloucestershire's modest 139 for nine, but superb bowling from Saxelby and Muttiah Muralitharan, who gave away just 16 runs in his four overs, ensured it was enough as the Steelbacks were restricted to 131 for eight.
The visitors were always struggling after being reduced to 18 for four, but Kyle Coetzer, with 44 from 38 balls, led a recovery until he was bowled around his legs by Muralitharan.
After being put into bat by Northamptonshire skipper Alex Wakeley, Gloucestershire made 46 from the six powerplay overs for just the loss of Hamish Marshall, who miscued a pull off David Willey to Con de Lange at mid-on.
However, spinners James Middlebrook and De Lange slowed the Gloucestershire momentum in the middle overs and the home side never really broke free from the stranglehold in the rest of the innings.
Williamson, in his last home match before departing for New Zealand's tour of the Caribbean, struck five boundaries in his 39 before he pulled Middlebrook to deep midwicket, where Rob White took a low catch.
Alex Gidman was also caught on the midwicket boundary by David Willey off De Lange, and it became 106 for four in the 16th over when James Fuller, who had hit two sixes in his 18, holed out to White at long-on to give Middlebrook his second wicket.
Jack Brooks accounted for Jack Taylor, caught at midwicket by De Lange, and Cockbain was taken at long-off by Coetzer from Chaminda Vaas's bowling, having struck the Sri Lankan for a straight six off the previous delivery.
A further three wickets fell in the last three overs as Ed Young and Dan Housego were run out and Jon Batty was caught at third man by Coetzer off Brooks.
Gloucestershire's total looked a little below par, but the home side took control of the game by reducing the Steelbacks to 18 for four inside four overs of their reply.
Fuller had White caught behind off a defensive edge and Housego took a steepling catch at midwicket to dismiss Robert Newton off Saxelby, who then had Wakeley taken at cover by Cockbain in the same over.
Cameron White was the next to go, caught by Marshall at mid-off from Young's off-spin, but Middlebrook and Coetzer then rallied the innings with a partnership of 54 in 51 balls.
Middlebrook had contributed 23 when he mistimed a drive at Williamson's off-spin and Muralitharan ran in from short third man to take the catch.
Coetzer hit sixes off Taylor and Williamson to keep the game in the balance, but it started to swing back Gloucestershire's way when he was bowled while trying to sweep Muralitharan, which made it 96 for six in the 16th over.
Saxelby returned at the Jessop Stand End and he effectively sealed the win by bowling Willey and having David Murphy caught at cover by Marshall.