|Bristol (17) 28|
|Tries: Lemi 2, Eadie Cons: Henson 2, Pens: Henson 2, Robinson|
|Worcester (22) 29|
|Tries: Betty, Penalty, Vuna, Biggs, Annett Cons: Lamb 2|
Worcester forward Niall Annett's late converted try secured victory over Bristol as the Warriors forged a narrow lead in the first leg of the Championship play-off final.
Former Worcester winger David Lemi scored two tries against his old club.
But Worcester outscored the hosts five tries to three for a victory margin that would have been greater had Ryan Lamb not missed several kicks at goal.
Bristol's Gavin Henson kicked 10 points before suffering a broken shin.
Henson had to be taken off on a stretcher late in the second half.
Bristol will be without both him and former Wales captain Ryan Jones, who suffered a recurrence of a shoulder injury, for the second leg on Wednesday, 29 May.
Worcester, who had lost both games to Bristol during the regular Championship season, led 22-17 at the end of an incident-packed first half at Ashton Gate which brought five tries, a penalty try and two yellow cards.
|Past Championship play-off record|
|Bristol: 2010 (finalists - lost 38-16 to Exeter)|
|2012 (semi-finalists - lost 63-53 to Cornish Pirates)|
|2014 (finalists - lost 48-28 to London Welsh)|
|Worcester: 2011 (promoted - beat Cornish Pirates 46-32)|
After former Wales international Henson followed his early penalty by pulling wide his second attempt, Sam Betty's pushover try - his 13th in the Championship this season - earned a 5-3 lead for the visitors.
Bristol number eight Mitch Eadie then burst through to go over close to the posts, Henson converting.
But the first of Bristol's two yellow cards, for Gaston Cortes, was closely followed by a penalty try, converted this time by Lamb.
And, after Anthony Perenise had also been sin-binned, briefly reducing Bristol to 13 men, Cooper Vuna went over in the left corner for Worcester.
Lamb missed with that kick and again with a penalty attempt which would have given Worcester a 10-point lead.
Instead, when Lemi went in at the right corner, Henson converted from the right touchline to haul it back to 17-17.
But Tom Biggs had the final word of a breathtaking first half when he came off the right wing to go in to the left of the posts, Lamb again missing, his fourth off target effort out of five.
The scoring was a lot less frenetic after the break, with only two tries, as tension grew.
Chris Pennell missed with a long-range penalty attempt before Henson was successful with his fourth kick of the night to move Bristol back within two points at 22-20 behind.
Henson missed with another penalty before Lemi's late try, which Nicky Robinson could not convert.
Robinson was then successful with a penalty and it looked as though Bristol would take a lead into the second leg.
But Annett's pushover try from the last play of the game, converted by Lamb, earned Worcester their single-point advantage to take back to Sixways.
Bristol director of rugby Andy Robinson told BBC Points West:
"What a great statement from both sides. It was a fantastic game of rugby.
"Worcester tactically dominated us early on. They set the tone with their pushover try but I was very pleased with our second-half performance. I'm just disappointed we weren't able to see it through.
"It was a game of small margins like we thought it would be. We've got to be able to dust ourselves down but I'm confident about playing away from home."
Worcester Warriors director of rugby Dean Ryan:
"It's half-time in the tie and it is pretty tight. It was a bold move for Bristol to go for home advantage and they wanted to put it on us in the first 40 minutes.
"We knew we had to come out and really attack it and the lads did a great job. Then, in the second half, we stood pretty firm. Bristol threw everything at us.
"We couldn't get field position and Henson's kicking was killing us, but we stood firm and saw it out. To finish like we did with a little bit of a show of defiance I thought was outstanding."
Bristol: Wallace; Amesbury, Maule, Henson, Lemi; Morgan, Peel; Traynor, Brooker, Cortes, Townson, Sorenson, Jones, Lam, Eadie.
Replacements: Crumpton, Perenise, Glynn, Mama, Kessel, N Robinson, Tovey.
Worcester: Pennell; Biggs, Grove, Mills, Vuna; Lamb, Bruzulier; Rapava-Ruskin, Creevy, Schonert, Thomas, Percival, Williams, Betty, Van Velze.
Replacements: Annett, Bower, Rees, Senatore, Shillcock, Fatiaki, Howard.
Referee: Wayne Barnes.