Foster also tried fighting with Heavyweights often, but with very little luck. He was the owner of very long arms, and a very tall boxer, physical attributes which helped him get established as a long standing champion.
Foster started his professional career on the night of March 27, 1961, against Duke Williams[?], in Washington, DC, winning by a knockout in two rounds. The first 12 bouts of his career were spent campaigning in the United States' Eastern coast and in Canada. In his tenth bout, he made his first of multiple forays into the Heavyweight division, and suffered his first loss, at the hands of Doug Jones[?] by a knockout in the eighth round.
Three more fights back in the States resulted in quick knockout wins for him, and then, in 1964, he made his second attempt at entering the Heavyweight rankings, being knocked out in the seventh by future world Heavyweight champion Ernie Terrell[?]. He finished the year by posting three more knockout wins at Light Heavyweight, two of them on one night: November 11. That was the night that Foster's first fight of note as a Light Heavyweight took place: Minutes after knocking out Don Quinn[?] in the first round, he stepped up in the ring again and faced former world title challenger Henry Hank[?]. He beat Hank by a knockout in the tenth.
In 1965, he had five fights, winning four and losing one. He beat Hank again, by decision in 12, and lost to the late Zora Folley[?], by a decision in ten, in another attempt at joining the Heavyweight top ten.
By 1967, Foster, although his attempts to become a top Heavyweight were being frustrated, was a ranked Light Heavyweight. He decided to stick to the Light Heavyweight division for the time being, and he won all seven of his fights, six by knockout. Among the fighters he beat were Eddie Cotton[?], Eddie Vick[?] and Sonny Moore[?]. After defeating Moore, Foster was the world's number one ranked Light Heavyweight challenger.
In 1968, Foster got his first shot at a world title. At Madison Square Garden in New York, on the night of May 24, Foster became world champion by knocking out the also late Dick Tiger[?] in four rounds. Tiger had been a two time world Middleweight champion and was defending his world Light Heavyweight crown that night. Then, Foster decided to try on the Heavyweights once again, and he beat future George Foreman victim Charlie Polite[?] by a knockout in three. He ended that year defeating Vick again, and his future world title challenger Roger Rouse[?], both by a knockout.
In 1969, he began by rising off the canvas to knock out Frank De Paula[?] in the same first round and retain his belt. It is believed that was the first time ever a boxer won a world title fight in the first round after being floored in that same round. It is also believed that that fight is one of only two times that's happened, the second time being in 1984, when Juan Kid Mesa[?] rose off a knockdown to dethrone world Jr. Featherweight champion Jaime Garza[?] in the same first round too.
In 1970, Foster made two more trips to the heavyweights. In the first, he beat fringe contender Cookie Wallace[?] in six rounds by knockout. This was followed by a return to the Light Heavyweight division to defend his title against Rouse. Infuriated by some comments that Rouse's manager had made before the bout concerning the fact that even thru Foster knocked out Rouse in their first bout he was not able to drop him, Foster dropped Rouse five times en route to a fourth round knockout victory. A knockout in 10 to retain the battle against Mark Tessman[?] followed, and then he was given the chance to challenge for the world's Heavyweight title. Facing world champion Joe Frazier on the night of November 18 in Detroit, he was knocked out in two rounds.
After defeating Hal Carroll[?] by a knockout in four rounds to defend his crown, the WBA stripped him of the title, but he kept being world champion on the WBC. Foster became enraged at the WBA, which proceeded to have Vicente Rondon[?] of Venezuela and Jimmy Dupree[?] fight for the world title. Rondon won, becoming the second Latin American world Light Heavyweight champion (after Jose Torres), and Foster set his eyes on him. Foster went on defending his WBC world title, and he defeated challengers Ray Anderson[?], Tommy Hicks[?] and Brian Kelly[?]. Of those three, it was Anderson who was the only one to last the 15 round distance with Foster.
Foster and Rondon met in Miami on April 7, 1972, in an unificatory bout. Foster became the undisputed world champion once again, by knocking Rondon out in the second round. In his next fight, he used what many critics have called one of the best punches in history to retain his title by a knockout in four against Mike Quarry[?]. He then went up in weight and faced former and future world Heavyweight champion Muhammad Ali, in what was legendary referee Mills Lane's first bout of note as a referee. Foster lost to Ali by a knockout in the eighth.
In 1973, Foster retained his title twice against Pierre Fourie[?], both by decision. Their second fight had a distinct social impact because it was fought in Apartheid ruled South Africa, Foster being Black and Fourie being White. Foster became a hero to South African Blacks by beating Fourie the first time around, and in their rematch, the first boxing fight in South Africa after Apartheid featuring a White versus a Black, he cemented that position by defeating Fourie on points again.
His last defense as world Light Heavyweight champion came in 1974, when he was dropped by Argentinian Jorge Ahumada[?], but managed to keep the title with a draw. After that, he announced his retirement, leaving the world's Light Heavyweight championship vacant.
In his retirement, this former world champion decided to join the New Mexico police, where he would become sheriff of Albuquerque.
Foster had a record of 56 wins, 8 losses and 1 draw, with 46 wins coming by knockout.