Andrea Costa scored the only goal of the game to give Sampdoria all three points from their trip to AC Milan this evening.
Milan dominated the first half and created numerous chances to break the deadlock.
However, Kevin-Prince Boateng, Robinho and Mario Yepes were all guilty of missing opportunities from close range.
They continued to control proceedings after the restart, but once again found keeping their efforts on target difficult.
Their failure to do so was punished against the run of play with 58 minutes played. Fernando Tissone swung over a corner which was met by Costa, who sent the ball into the home net from close range.
Milan laid siege on the away goal in the closing stages, but goalkeeper Sergio Romero and his defence held firm to claim the victory.