Deontay Wilder produced another sensational finish to see off Luis Ortiz in 10 titanic rounds in New York.
The 'Bronze Bomber' had his challenger down in the fifth round and twice in the decisive onslaught but was in all sorts of trouble himself in the seventh.
Wilder was staring a disastrous defeat in the face as Ortiz almost finished him off, only for the WBC heavyweight world champion to cling on and then turn the fight on its head, eventually moving to 40-0-KO39, just over two minutes into the 10th.
It might not have fired out the expected warning to Anthony Joshua but in front of a sold-out Barclays Center, Brooklyn, it had an air of 'AJ's epic win over Wladimir Klitschko at Wembley Stadium.
Wilder had always said Ortiz, unbeaten himself, was far and away his biggest test and so it proved, the Cuban making a bright start with the champion looking as nervous as he was focused.
Ortiz slipped straight into a smooth rhythm, the only one to land any combinations of note and although he did touch the canvas in the second round, this one was clearly a stumble.
Wilder's jab took a while to get going and with his famous right missing more than it hit, the New York crowd delivered the first serious blow of the night, with a chorus of boos as neither fighter went on the offensive.
Ortiz was the first to try and find, if not light, the heavyweight touch paper, a left hook and a straight right sneaking in, showing there were gaps in the 6ft 7in giant's guard.
Wilder though, was the first to set the sparks going and had his man down in the fifth. A gentle dabbing jab took the Cuban's attention and the ferocious right that landed flush on his forehead had 'King Kong' down for the first time in his professional career.
Ortiz made it up and with less than 10 seconds left, Wilder was unable to go for the familiar finish but after such a cagey opening, he had, at last, started to stamp his authority on proceedings.
It did not last long though, because despite being caught with another hard right, Ortiz then troubled his man with a classic countering right, then a big left hook, leaving Wilder clearly stunned, somehow still on his feet and able to make it to the safety of his corner.
The judges could well have scored that 10-8 in Ortiz's favour but with Wilder restoring his equilibrium he was at least able to trade blows in a wild finish to the eighth.
The ninth round had more boos from the crowd but with his trademark right cocked throughout, Wilder was either appeasing the Brooklyn boxing fans or realising that maybe Ortiz's efforts were taking their toll.
Either way, the Wilder knockout was not far away, despite Ortiz making the sharper start of the 10th, his left-right combination sneaking in.
But, when he tried it again that right was poised and responded with pure power, wobbling then toppling 'King Kong'. Somehow Ortiz beat the count but with Wilder on the rampage, the WBC holder put him over again, before the referee stepped in.