West Ham 1-3 Bolton
Two Robert Green errors and a stunning Matthew Taylor free-kick secured victory for Bolton at West Ham.
The Hammers keeper gifted Bolton their opener when he dropped a hopeful cross at Kevin Davies' feet and the striker poked the ball into an empty net.
Green then failed to hold the ball after saving Gretar Steinsson's volley and Gary Cahill was on hand to tap in.
Carlton Cole headed in from a corner to give West Ham hope but Taylor smashed in a free-kick to secure the win.
Although Bolton's tactics were defensive at times it was probably no more than they deserved from a disciplined performance.
It might have been very different as West Ham's confidence was evident early on, as they looked to continue secure third successive league win.
Their passing game quickly had Bolton on the back foot, with on-loan left-back Herita Ilunga a particular danger with some strong running.
Carlton Cole also looked a threat but failed to keep his shot down after a sharp turn.
However, it was Bolton who created the first real opening and Johan Elmander should have done better than to direct a tame shot straight at Green.
Back came West Ham and Ilunga almost worked his way through on goal but was denied at the last by Jlloyd Samuel.
And as Bolton sat back the hosts looked on the verge of making their dominance tell as shots came in from David di Michele and Valon Behrami.
But then in the space of four minutes, the game was turned on its head.
First Green came out to collect a high ball but dropped it for Davies to gratefully slot home.
And then the unfortunate keeper failed to cling on to Steinsson's well-struck effort and Cahill was quickest to the loose ball to make it 2-0 to the visitors.
West Ham tried to push on and set about getting themselves back in the game, but their earlier swagger had gone and they looked stunned.
The hosts must have received a stern talking-to at half-time as they emerged after the interval with renewed fight.
And they almost halved their deficit when Carlton Cole's curler seemed to be heading for the top corner until Jussi Jaaskelainen clawed it away and onto the post.
Bolton hit back and Gavin McCann went close with a fierce strike before a Matthew Upson backpass nearly heaped more embarrassment on Green.
Then from a set-piece West Ham gave themselves a lifeline when Upson headed back a corner for Cole to nods in, with the help of a slight deflection.
West Ham were now in the ascendancy as Bolton sat back trying to protect their lead.
But despite having much more of the ball, the hammers were finding it impossible to break their opponents down.
Instead it was Bolton who struck again when Taylor's swerving 25-yard free-kick easily beat Green and ensured Bolton left Upton park with all three points.