Evander Holyfield launched his comeback bid with a second-round stoppage of journeyman Jeremy Bates in Dallas.
The 43-year-old former undisputed heavyweight champion had Bates in trouble at the end of the first round before the bell sounded.
Holyfield continued his onslaught at the end of the second and the referee stepped in to stop the fight with just four seconds of the round remaining.
The American is hoping to claim an unprecedented fifth world title.
"I'm so glad to get the opportunity to get back in the ring and show the people that I wasn't not a boxing man because I'm old," said Holyfield.
"I was able to do the things that I haven't been able to do in five years. I was able to slip punches, I was able to use my foot speed, I was able to go in and out."
Holyfield was fighting for the first time since losing to Larry Donald in November 2004, a defeat that was so lacklustre that New York boxing officials revoked his licence.
He plans to have a title fight in 2007 and to have all the belts around his waist, "by the time that Olympics comes," in 2008.
Insurance salesman Bates, who now has a 21-12-1 record, had quit the ring before Holyfield came calling.