Jubilant Manchester City celebrated a famous victory in the first Manchester derby at their new Eastlands home.
Kevin Keegan's side punished schoolboy defending from United to register their first home win in almost five months.
After failing to register a win at the City of Manchester Stadium in 11 previous attempts, they ended their horrid run in breathtaking style and avenged two defeats earlier this season at Old Trafford.
Keegan is determined to use the victory, only the second in 17 Premiership matches, as a platform to climb into the top half of the table.
"We needed to lay the ghost in this stadium were we had won only two league games," he said.
"Sometimes you believe there is something wrong and maybe there is a curse. It has lifted and we can now call it home.
"The 4-1 scoreline flattered us, but nevertheless it is in the history books." Sir Alex Ferguson, whose side have picked up only two points from their last four Premiership games, was critical of his side's defensive play.
"It was sloppy defending, and it has been like that for two months.
"We are not doing even the simple things like clearing our lines and dumping the ball. We are showing far too much nervousness." City made a dream start taking a third minute lead when Robbie Fowler breezed past Phil Neville to fire home a shot low to the right of keeper Tim Howard.
Cristiano Ronaldo struck an upright for United, but City doubled their lead in the 32nd minute when Jonathan Macken seized on further slack defensive play to score with a neat shot on the turn against the team where he started his career.
Paul Scholes quickly halved the score with a low drive and United might have equalised before the break had Ronaldo not hit the crossbar with a curled shot.
City scored their third goal in the 73rd minute after another piece of bad defending from United.
Mikael Silvestre failed to control a throughball allowing substitute Trevor Sinclair a clear route to goal as he squeezed the ball past Howard.
Then in stoppage time came the icing on the cake when Shaun Wright-Phillips scored a brilliant solo effort following a run from the halfway line.