Wayne Rooney scored twice as Manchester United defeated 10-man Manchester City in a thrilling FA Cup third-round tie.
Rooney gave United an early lead with a header from Antonio Valencia's cross.
Vincent Kompany was sent off for a two-footed tackle on Nani before Danny Welbeck volleyed home and Rooney headed in the rebound from his own penalty.
City fought back through an Aleksandar Kolarov free-kick and a Sergio Aguero goal, after an error from the returning Paul Scholes, but United held on.
Scholes, whose decision to come out of retirement was announced an hour before kick-off, played the final 30 minutes of an astonishing game in which both sides had strong penalty appeals turned down in the second period.
With the score at 3-1, referee Chris Foy denied United a spot-kick for a mis-timed tackle by Kolarov on Valencia and, after Aguero's strike, City thought they should have been given a penalty when Kolarov's cross struck Phil Jones on the arm.
City even had the chance to equalise in the final minute of stoppage-time when Kolarov's free-kick was saved by Anders Lindegaard before a City corner was cleared by the head of Rooney.
The home side's second-half display belied United's numerical advantage, but the visitors held on for a victory that went some way towards exacting revenge for City's 6-1 Premier League victory at Old Trafford in October.
