Lamont Peterson, showing no rust after a 14-month layoff, stopped Kendall Holt in the eighth round to retain the International Boxing Federation light-welterweight crown.
Peterson, once a homeless child on the streets of the US capital where he defended his title, improved to 31-1-1 with his 16th stoppage inside the distance when referee Tony Weeks stopped the fight after 1:42 of the eighth.
Holt fell to 28-6 with his fourth loss in seven fights when Peterson stunned him with a right to the head and finished him off against the ropes with a flurry of unanswered punches that prompted Weeks to jump between the fighters.
"That last time I caught him against the ropes, I just let my hands go," Peterson said. "I let him have everything and I knew I had him."
Peterson, 29, ended a 14-month layoff following a positive doping test for synthetic testosterone that scrapped a planned fight with England's Amir Khan last May. Holt, 31, ended an 11-month layoff after right shoulder surgery.
Peterson, who blamed his positive test on treatments for low testosterone, was stripped of the World Boxing Association title, one of two he took from Khan in a controversial victory at Washington in December of 2011.
But the IBF, after hiring its own medical expert and conducting more tests that found no performance advantage, kept Peterson as champion, giving him the chance to defend his title and reputation.
The bout brought only $37,500 for Peterson and $12,500 for Holt, but could offer Peterson a possible big-money unification showdown.
Unbeaten American Danny Garcia, 25-0 with 16 knockouts, will defend the WBA and World Boxing Council crowns in April against US southpaw Zab Judah (42-7 with 29 knockouts), who rejected a Peterson fight for the bigger Garcia payday.
"Danny Garcia holds that belt. I still think I'm the WBA champion," Peterson said. "I would like to see that fight."
After a cautious start, Holt pressed the attack to start the fourth round, keeping Peterson on the defensive, but the champion deflected the worst of Holt's blows and answered with a hard right that sent Holt to the canvas.
The challenger crumpled and fell forward onto his knees, but rose and answered the count moments before the end of the fourth.
Peterson punished Holt for most of the fifth, a weary Holt pinning him against the ropes with his body at one stage but gaining little relief from hammering punches to the head and body.
"When he did hit me with one of his punches and it was right on the button and I felt nothing, I knew I had him," Peterson said.
In the sixth, Peterson kept Holt to the ropes and landed more than a dozen rapid-fire punches to only one in response from Holt, who kept his arms raised as cover and took a knee, rising to finish the round but clearly in trouble.
Holt hugged, evaded and jabbed to keep Peterson at bay in the seventh but in the eighth, Peterson stunned Holt with a solid right to the head and launched a series of punches with Holt on the ropes until Weeks stepped between the fighters to end the punishment.