[3][4][5] He fought Heavyweight greats such as Muhammad Ali, Joe Frazier, Jerry Quarry and Ron Lyle;[3][6][7][8] he also notably beat Joe Frazier as an amateur to qualify for the Olympics but was later replaced due to a hand injury.

Mathis turned professional in June 1965 with a second round knockout victory over Bob Maynard.

[11] The title fight was held on March 4, 1968, in New York's Madison Square Garden against "Smoking" Joe Frazier, his old rival.

[citation needed] It reported Mathis worked in the trucking business after he retired from the ring.

[citation needed] Mathis had various health problems in later years, including two strokes, a heart attack, and kidney failure.