West Brom 2 Birmingham 0
West Brom gave themselves a relegation lifeline as goals from Neil Clement and Kevin Campbell moved them off the bottom for the first time since the end of November.
Baggies manager Bryan Robson had described the derby as a must-win encounter and his side began the day eight points adrift of safety.
But they responded in a positive manner to the challenge in deservedly registering what was only their third league win of the campaign.
Albion had a greater desire and hunger for the battle and no-one personified this more than former Blues striker Geoff Horsfield who was a constant threat with his physical presence.
Zoltan Gera and Jonathan Greening impressed on the flanks as the Baggies avenged the 4-0 mauling at St Andrews in December.
It was Blues first derby defeat in 11 matches with Aston Villa, Wolves and Albion since returning to the top flight and they can have few complaints.
But on this evidence Birmingham have to be careful not to be dragged back into the relegation fight themselves and midfielder Stephen Clemence was one of the few players to emerge with much credit.
After a tame first half, the Hawthorns erupted after 53 minutes when Clement headed Albion ahead.
Gera chased down what appeared to be a lost cause to win a corner for his side and, from the resulting cross by Richardson, Clement made no mistake with a downward header after losing his marker Diao.
Birmingham tried to retaliate and within 60 seconds only the woodwork denied Emile Heskey an equaliser.
Lazaridis did well with his back to goal to turn and send over a right-footed cross and Heskey's glancing header clipped the post.
But Albion were still showing more passion and desire and after 64 minutes they doubled their lead.
Horsfield's persistence won him the ball off Ireland captain Kenny Cunningham before releasing Greening on the left flank.
He steadied himself before delivering a deep cross and Campbell was perfectly placed at the far post to volley home.
Campbell headed inches wide from a Horsfield cross who then left the field to standing ovation from both sets of fans in the closing minutes with the points safely secured.
PA