Bryan Robson's first match as West Brom boss ended in defeat as his former club Middlesbrough came back to haunt him at The Hawthorns.
The first goal conceded under Robson was one to forget, as defender Darren Purse turned Jimmy Floyd Hasselbaink's cross into his own net.
Robert Earnshaw slotted in from close range after good work by Cosmin Contra to bring West Brom level.
But Boro winger Boudewijn Zenden scored the winner with a looping header.
Baggies boss Robson could not have been expecting any favours from the club he managed for seven years, and he certainly did not get any.
Boro keeper Mark Schwarzer, who was signed by Robson, gave an outstanding performance.
In the first half he made a number of excellent saves, the finest being a double stop from Ricardo Scimeca and then Earnshaw.
But in an open game, Boro were also creating opportunities as well as keeping their opponents out.
The lively Stuart Downing was proving a handful with his pace and direct running.
The winger almost opened the scoring after a neat one-two with Franck Quedrue, but fired wide.
The visitors were also unlucky not to earn a penalty after Mark Viduka appeared to be tripped by Scimeca.
But on 32 minutes, West Brom went behind as Hasselbaink crossed dangerously and Purse stuck out his leg only to see the ball roll into his own goal.
The lead lasted just five minutes though.
Excellent work from Contra on the right flank resulted in a low cross which an unmarked Earnshaw gratefully converted.
Just five minutes after the break, the excellent Downing provided a telling contribution.
His cross found Zenden and the Dutchman lopped a header over the stranded Russell Hoult.
But there was no quick reply this time for the Baggies as Kanu shot wide of Schwarzer's left-hand post.
Robson made a surprising double substitution on the hour, replacing Zoltan Gera and Earnshaw with Geoff Horsfield and Rob Hulse.
Neil Clement wasted a good free-kick chance in the 62nd minute when he blazed over from the edge of the Boro box.
The Baggies were given another set-piece opportunity when Riggott brought down
Kanu just outside the box.
Once again they wasted it by failing to muster a shot as the Boro defence bustled the ball clear.
Viduka had a chance to make the game safe in the 72nd minute but he shot over the bar in the box from Ray Parlour's cross from the right.
As time ran out, West Brom looked set to snatch a point as Horsfield rolled a cross into the area.
The waiting Kanu appeared set to tap the ball in but somehow managed to spoon the ball over the bar from two yards out.