Mexico's Antonio Margarito stopped countryman Manuel Gomez just 74 seconds into the first round to retain the WBO welterweight title in Las Vegas.
Manuel Gomez takes another blow from Antonio Margarito
Margarito improved to 33-4, including 25 knockouts, by hitting Gomez with a series of powerful right hands that felled the challenger.
Margarito is chasing a bout with Floyd Mayweather Jr, former welterweight champion Zab Judah or Shane Mosley.
He said: "Floyd has to recognise me as one of the great welterweights."
American Brian Viloria retained his World Boxing Council light flyweight title with a 12-round unanimous decision over Mexico's Jose Antonio Aguirre.
And WBO strawweight champion Ivan Calderon remained unbeaten, improving to 25-0 with a unanimous decision over former WBC champ Isaac Bustos.