Vitali Klitschko defended his WBC heavyweight championship with a first-round knockout of Odlanier Solis in Cologne. Cuban challenger Solis appeared to have matched his Ukrainian opponent for much of the three minutes, but was caught on the temple by a right hand and staggered to the ground.
He clutched at his right knee as soon as he landed and, though he tried to scramble back to his feet using the ropes for support, referee Jose Guadalupe Garcia stopped the fight.
Klitschko appeared angry at his opponent's withdrawal, ready for more of a challenge, and the crowd also jeered but it quickly became apparent that Solis was struggling badly with a leg injury suffered as he fell.
The defeat is the first of Solis' career after 17 successive wins, 12 by knockout. For 39-year-old Klitschko, it was a 42nd win and a 39th KO in a 44-fight career.
Klitschko told Sky Sports 1: "Solis was very fast but a hard punch worked for me.
"I have the nickname Iron Fist - I'm so sorry for everyone who wanted to see a long fight but I hit him pretty hard with my right hand and it was enough.
"It will be very interesting to listen to what the doctors say after the medical exam. But the punch was really hard.
"I was prepared to show a really good fight but this is boxing - one punch, the game is over."
Brother Wladimir, who holds the other three world titles in the division, was in Vitali's corner and said: "I'm very proud. Solis was very good, he was actually catching Vitali, but Vitali just hit the button. I'm very proud of my brother that he did it this way."
England's David Haye will take on Wladimir Klitschko later this summer.
And Vitali Klitschko said after the fight: "I have a feeling nobody in the world can beat me.
"David Haye will fight my brother because against me it would be very short and painful."
Wladimir Klitschko added: "Haye chose to fight the younger one, the weaker one - I'm next!"