A double strike by Eidur Gudjohnsen and a Gianfranco Zola special shot Chelsea into third place in the Premiership as Birmingham were sunk at Stamford Bridge.
It took just two minutes for the Londoners to tear the Midlanders apart. An extraordinary counter-attack saw the ball stroked from left to right with Zola the architect with a deft back-flick to Jody Morris, who played in Gudjohnsen wide on the right.
The Icelandic striker ploughed into the penalty area and drove a low shot across Nico Vaesen's path to plant the ball into the far corner.
The mercurial Zola then prompted Gudjohnsen to his second goal with an almost identical finish on 31 minutes.
The game was too far gone for Birmingham before half time, when man of the match Zola helped himself to his ninth goal of the season.
Graeme Le Saux won the ball off Jeff Kenna, wide on the right. The ball was steered into the path of Zola, who blasted the third goal, past Vaesen in off the inside of the right hand net.
Birmingham upped the temp in the second half, but Chelsea had too much of a cushion.
A Emmanuel Petit left-footer crashed off the crossbar and Zola had a scuffed shot kicked off the line by Birmingham's best player Paul Devlin.
It was Devlin who had the best chance for the Midlands side when in the first half he beat the offside trap and found himself in the Chelsea area.
However, not realising how much time he had, he screwed the ball wide of Carlo Cudicini. Stern John was lively for Birmingham, but the Londoners had too many players on top form.
"We were given a bit of a doing," admitted Birmingham boss Steve Bruce. "I have to hold my hands up and say Chelsea were far too good for us today.
"They have talented players but our defending was of a schoolboy level, and you can do that at this level. We showed some spirit in the second half, but the basic elements of defending were missing.
"On this showing, Chelsea must have a shot of the title, they have shown consistency of late and have some very talented players," he added.
Chelsea boss Claudio Ranieri was delighted with his team: "We were fantastic today, especially in the first 30 minutes.
"This win will do wonders for our confidence. Zola, at this minute is irreplaceable and our target is to get into the top four in the league."