MANNHEIM, Germany — Wladimir Klitschko defended his IBF heavyweight crown today by stopping American Hasim Rahman in the seventh round at SAP Arena.

Klitschko, who has not lost in more than four years, hit the shorter Rahman at will throughout, and after landing a left-right-left combination against the cornered American, the referee stepped in to end the contest. Rahman didn't appear upset.

Klitschko had knocked down Rahman in the previous round with successive left hooks.

The technical knockout in Klitchsko's sixth defense of the IBF belt — and third this year — improved the Ukrainian-born fighter to 52-3 with 46 KOs.

Rahman, the two-time heavyweight champion who stepped in as a replacement opponent last month, struggled to get inside the taller Klitschko's reach, and dropped to 45-7-2.

The fighters started out fast and light on their feet, but it soon became apparent that Rahman was struggling to overcome the 3½-inch height advantage enjoyed by the champion. Rahman had to lean in drastically, and Klitschko easily fended off his punches.

Rahman did little more than lean on the ropes for a time and guard his face as Klitschko sought his opening.

Rahman looked reinvigorated in the fourth round, using his whole torso to make ambitious attacks, often connecting with Klitschko's body.

But he rarely landed blows above Klitschko's shoulders, and the consequences were clear when Klitschko dropped Rahman early in the sixth with two hard lefts to the side of his head.

Rahman got up but spent the remainder of the round in the corner, taking a sustained beating.

Another flurry at the opening of the seventh ended Rahman's challenge.

Klitschko also retained the minor WBO and IBO belts.

Klitschko was originally scheduled to face Alexander Povetkin (16-0), but the Russian pulled out with an ankle injury. Rahman, who won the WBC and IBF belts from Lennox Lewis in 2001 and the vacant WBC belt in 2005, arrived in Germany on Monday and declared he was in top shape.

On the undercard, former heavyweight champion Riddick Bowe made a modest comeback with an eighth-round decision over Germany's Gene Pukall. It was just the third fight in a decade for the 41-year-old American and his first in three years.

Bowe (45-1, 33 KOs) had been training in Germany since September in an effort to get his stamina up and his weight down. The work paid off in the ring, where he kept up with the 33-year-old Pukall (14-13-2, 12KOs) and bested him with a stream of careful head shots.