Bristol scrum-half Shaun Perry had a superb game
Worcester: (11) 11
Pens: Drahm 2
Bristol: (18) 41
Tries: Llewellyn, Robinson 2, Morgan, Perry
Cons: Strange 2
Pens: Strange 4
Bristol breezed to their first ever victory at Sixways as woeful Worcester suffered an opening-day nightmare.
Tries from veteran Welsh lock Gareth Llewellyn and wing Lee Robinson gave the visitors an 18-11 half-time lead.
Phil Murphy grabbed Worcester's only try but their set-piece disintegrated and Bristol took full advantage.
Robinson's second try with eight minutes left sealed victory before two late scores from Craig Morgan and Shaun Perry put the seal on a remarkable win.
Fly-half Jason Strange added 16 points with the boot as Bristol earned their first bonus-point win for two seasons.
Worcester's misery was compounded by injuries to centre Dale Rasmussen, who was taken to hopital after a clash of heads with Bristol's Tongan full-back Josh Taumalolo, and hooker Ben Gotting.
Worcester's director of rugby John Brain
"I think by the standards that we set ourselves that was an unacceptable level of performance," he said.
"I'd like to apologise to our supporters who paid good money to watch this match.
"I think that everything that Bristol did came off and I thought that we were
out-muscled and out-mauled."
Bristol head coach Richard Hill
"I'm slightly lost for words with the win because it was totally unexpected.
"But it is a perfect start to the new season so I've got to congratulate the
players because I thought they were very efficient while not being flash.
"Virtually everything we did was very clinical. All the things that you wish
a side to do, we did without any stars in that side. It was a very good team
Worcester: Best; Delport, Rasmussen, Whatling, Garvey; Drahm, Runciman; L Fortey, C Fortey, Horsman; Blaze, Murphy, Sanderson (capt), Harding, Horstmann.
Replacements: Taumoepeau, Gotting, Gillies, Quinnell, M Powell, Lombard, Tucker.
Bristol: Taumalolo; Robinson, Higgitt, Reay, Morgan; Strange, Perry; Hilton, Regan, Crompton; Winters, Llewellyn, Salter (capt), El Abd, Ward-Smith.
Replacements: Clarke, Lemi, To'oala, Lewis, O'Riordan, Gray, Pozzebon.
Referee: Dave Pearson (RFU)