Notts beat Birmingham by eight wickets
Alex Hales stars with 86 not out off 43 balls
Glamorgan beat Surrey with highest domestic T20 score at The Oval
Matthew Fisher, 17, takes 5-22 as Yorkshire defeat Derbyshire
Image source, Getty ImagesWarwickshire and England batsman Ian Bell: "Good luck to the reigning champs tonight @CricketingBears #YouBears @NatWestT20Blast"
Bell was part of the title-winning Birmingham Bears team in 2014, but he is not involved in tonight's opener against Nottinghamshire Outlaws at Trent Bridge.
We have our first six of the season, ladies and gentlemen, and it comes courtesy of the effervescent Phil Mustard as Northants continue to struggle to keep the home side in check at Chester-Le-Street.
England batsman Alex Hales plays for Notts tonight before he jets off to India to appear for Mumbai in the IPL. Zimbabwe international Brendan Taylor and South Africa bowler Vernon Philander are also selected.
Birmingham, the defending champions, are without England duo Ian Bell and Chris Woakes, but there's plenty of experience in their bowling attack, with off-spinner Jeetan Patel included in the team just a couple of days after reaching 500 first-class wickets.
Nottinghamshire: Hales, Wessels, B. Taylor, Patel, J. Taylor (capt), Smith, Mullaney, Philander, Ball, Fletcher, Gurney.
Birmingham: Chopra (capt), Porterfield, Lewis, Clarke, Evans, Javid, Ambrose, Patel, Barker, Wright, Rankin.
Notts have won the toss and will bowl first - live commentary on BBC local radio and BBC Radio 5 live sports extra.
Shahid Afridi makes his first contribution for Northants as he is handed the ball by skipper Alex Wakely for the eighth over of Durham's innings. But his leg-spin holds no terrors for MacLeod who adds two more fours to his impressive boundary tally as 10 come from the over.
However, Josh Cobb gets rid of the rampaging MacLeod as he has him caught at fine leg, having hit 12 fours in his 32-ball 60.
It brings captain Paul Collingwood to the crease, could this last season be his last chance to lift T20 silverware with the Jets?
Joe Burns' first innings for Middlesex does not last long as Gloucestershire's second Taylor - off-spinner Jack - has him caught just inside the rope at long-off by Hamish Marshall. Nick Compton, at the other end, is going well on 33 off 25 balls.
Desperate to know how your side are getting on in this season's T20 Blast? Fear not - you can do follow all of the action with the help of the BBC Sport app.
You can set up push alerts for your selected county, which will let you know about the key moments as they happen.
Image source, BBC Test Match SpecialA quick mud bath for our reporters ahead of Nottinghamshire Outlaws v Birmingham Bears!
BBC's Test Match Special: "Here's our T20 commentary team in final preparations. Join @CharlesDagnall, @henrymoeranBBC & @ejrainfordbrent at 615pm."
Image source, Scott Read/BBC SportLast year's beaten finalists Lancashire Lightning are still without a domestic T20 title, despite having reached the semi-final stage on five occasions since the competition's inception in 2003.
As you can see from this picture tweeted by BBC Radio Lancashire's Scott Read, Old Trafford is bathed in sunshine ahead of tonight's opening match against Leicestershire Foxes.
Image source, PAT20 debutant Matthew Taylor makes a vital breakthrough for Gloucestershire as he bowls Paul Stirling off the inside edge to end an opening stand of 65 with Nick Compton. Stirling hit six fours in his 24-ball knock and his departure brings Australian Joe Burns to the middle for his first innings for the visitors.
Calum MacLeod has raced to his 10th T20 half-century. The Scotsman flat-bats a ball between point and cover, while falling over, to hit Olly Stone for his fifth boundary of the sixth over, which included a first-ball no-ball.
Mark Stoneman will no doubt be kicking himself for getting out so cheaply on what seems like a good batting pitch.
Perhaps someone in the Middlesex camp is reading the live text and has sent a message to the players in middle, as both Paul Stirling and Nick Compton start to find the boundary, with 30 runs coming off the last two overs.
Compton has been gifted a big lifeline as he is dropped at mid-wicket on 24. That could be a very costly mistake...
Image source, Getty Images/BBCAmong all the Surrey stars, Jason Roy was the name on everyone's lips last summer as he notched up nine fifties in the competition and ended as the leading run-scorer with 677 runs.
The 24-year-old goes into the competition on the back of a 28-ball half-century, which helped his side chase down 216 in less than 22 overs against Leicestershire in the County Championship.
Roy has emerged as one of the most exciting talents in the game and has earned England recognition in the 20-over and 50-over formats.
Durham are rebuilding as Calum MacLeod sends David Willey for three consecutive fours before giving Olly Stone the same treatment, bringing out the reverse sweep early on in his innings.
MacLeod has a T20 international century to his name, hitting an unbeaten 104 off 76 balls for Scotland against Oman in 2012.
Unlike in the Big Bash, there are no flashing bails, but there are plenty of pyrotechnics and cheerleaders to keep the near 2,000 strong crowd happy.
Apparently, Glasgow-born MacLeod has more than one nickname. Highlander is understandable, but Cloudy? Can you enlighten us?
Image source, Getty ImagesThis is the 13th season of domestic Twenty20 cricket in England, and the second year in which the competition has been known as the T20 Blast.
There may not be the razzmatazz, huge crowds and financial rewards on offer here compared to the IPL or the Big Bash.
But, as BBC Sport's Gary Smee writes, there's plenty to look forward to and plenty of world stars arriving on our shores over the next three months.
Middlesex have made a leisurely start against Gloucestershire as Nick Compton and Paul Stirling trade singles, before the former hits the first boundary of the innings off James Fuller.
They will undoubtedly be looking to up the scoring rate in the first six overs during the powerplay, where only two fielders are allowed outside the circle.
Image source, Getty ImagesSo the T20 Blast is under way, and although some of the overseas stars are yet to arrive in England, some of the world's top talent will be appearing at a ground near you over the coming weeks.
So, which players are you most looking forward to watching in this season's competition?
Are you hoping for some "Boom Boom" from Shahid Afridi at Northants? A "Gayle-force" innings from Chris at Somerset? Or a "Big Show" from Yorkshire's Glenn Maxwell?
Get in touch using #bbccricket on Twitter or on the BBC Sport Facebook page.
Image source, Getty Images/BBCPakistan all-rounder Shahid "Boom Boom" Afridi has played plenty of county cricket in England, having previously spent time with Leicestershire, Derbyshire, Kent and Hampshire.
Having made just 116 runs at the World Cup earlier this year, the explosive batsman will be looking for an improvement in form to light up evenings in Northampton this summer.
Mark Stoneman becomes the first batsman dismissed in the 2015 T20 Blast competition, as South African bowler Rory Kleinveldt uproots the Durham batsman's middle stump.
What a start for the 2013 champions Northants.
Image source, @GloscricketAll over the country, BBC local radio teams are getting in position ahead of tonight's T20 Blast matches.
BBC Radio Bristol's Geoff Twentyman is presenting his Drivetime programme from Nevil Road, as Gloucestershire open their campaign at home to Middlesex.
Listen to live commentary of all tonight's T20 Blast matches via the Live Coverage tab.
So we're about to get things under way in our two early games.
Are you ready for Blast Off?