Lamont Peterson returned from a 14-month lay-off to stop Kendall Holt in the eighth round and retain his IBF light-welterweight title.
Peterson improved his record to 31-1-1 when referee Tony Weeks stepped in to end the fight with Holt taking heavy punishment, much to the delight of a partisan Washington crowd.
The 29-year-old was banned last year after a positive doping test for synthetic testosterone but the IBF, who hired a medical expert and conducted tests that found no performance advantage, allowed him to keep his belt and defend it.
He came under pressure from Holt in the fourth but Peterson deflected the best of his punches and answered with a hard right than sent Holt crashing to the canvas.
The punishment continued in the fifth and Peterson stepped up again in the sixth, a rapid fire burst of more than a dozen punches pushing Holt further and further back.
Holt entered into a hugging match in the seventh but in the eighth Peterson stopped him in his tracks with a right to the head and launched into a series of punches that put his opponent on the ropes until Weeks waved the fight over.
Peterson now wants to take on unbeaten American Danny Garcia, for the WBA title, one he was stripped of after beating Amir Khan in December 2011 in controversial fashion.
"Danny holds that belt, but I still think I am the WBA champion," Peterson said. "I would like to see that fight.
"When he did hit me with one of his punches and it was right on the button, I felt nothing. I knew I had him.
"That last time I caught him against the ropes, I just let my hands go. I let him have everything and I knew I had him."