Deontay Wilder defended his WBC heavyweight title with a ninth-round knockout of Eric Molina in Alabama.
The 29-year-old, who beat Bermane Stiverne in January to become the first American to hold a heavyweight title since 2007, is unbeaten in 34 fights.
Molina, 33, who had lost two of his 25 bouts, was knocked down in the fourth round and twice again in the fifth.
In the ninth a straight right spun him around and the follow-up punches sent him down again and ended the contest.
Wilder's victory over Stiverne at the start of the year remains the only time he has been taken to a full 12 rounds.
The 6ft 7in fighter could now target a meeting with Wladimir Klitschko - unbeaten since 2004 - who holds the other belts, and said this title defence would be the "first of many".