Hamburg, Germany (SportsNetwork.com) - Wladimir Klitschko easily kept his IBF heavyweight title with a fifth-round knockout of Kubrat Pulev on Saturday at Hamburg's O2 World arena.
Klitschko's devastating left hook dropped Pulev with under a minute to go in the round, the fourth time he knocked down the previously unbeaten Bulgarian.
Referee Tony Weeks stopped the count, signaling the end.
Klitschko (63-3, 53 KOs) remained unbeaten in his last 21 bouts since his last loss, to Lamon Brewster in 2004.
The 38-year-old Ukrainian also holds the WBA, WBO and IBO belts.
Pulev (20-1) was cut under both eyes in his first title fight.
He was knocked down for the first time by a left hook less than 1 1/2 minutes into the bout, then again almost as soon as he got up after losing his balance on another Klitschko left.
Klitschko wobbled him with a right early in the third round, then knocked him down again moments later.