Adams and Clark first joined together as a duo in April 2000 in World Championship Wrestling. Upon joining together as a tag team, Kronik assisted Vince Russo in his vision of a clean sweep for his New Blood alliance at the 2000 Spring Stampedepay-per-view. Adams and Clark interfered in the WCW World Tag Team Championship match, allowing the team of Buff Bagwell and Shane Douglas to win the title. While in WCW, Kronik moved between babyface and heel roles several times - holding the WCW Tag Team Championship twice. In the final months of WCW, Kronik became hired muscle, adopting the catch phrase "breakin' necks and cashin' checks", similar to the WWE's popular APA tag team. Their contracts were not picked up by WWF when WCW was sold by Time Warner.
In September 2001, Brian Adams and Bryan Clark each made their re-debut as a World Wrestling Federation tag team. Recruited by Stevie Richards, Kronik was called in to settle past differences Richards had with The Undertaker, stemming from the disbanding of Richards' stable, "Right to Censor" earlier that year. Kronik wrestled their first tag team match defeating Kaientai on the September 20, 2001 episode of SmackDown and their last tag team match for WWF a few days later at Unforgiven, losing to then WCW Tag Team Champions The Brothers of Destruction. After two dark matches, four appearances on Raw and Smackdown and a pay-per-view appearance, Clark was released from his contract for being unconditioned and unsafe during their PPV match, while Adams began working for the Heartland Wrestling Association, which served as WWF's developmental territory, for conditioning. Adams requested his release from the WWF in November 2001, he and Clark reformed KroniK made a number of appearances on the independent circuit, most prominently for World Wrestling All-Stars and All Japan Pro Wrestling. During their time in AJPW, they defeated Keiji Mutoh and Taiyō Kea for the World Tag Team Championship on July 17, 2002. KroniK were later stripped of the title due to contract problems. They wrestled their last match together in January 2003, losing to Goldberg and Keiji Mutoh.
Following their WWF departure, KroniK joined up with World Wrestling All-Stars and appeared on their second pay-per-view: Revolution defeating Navajo Warrior and Ghost Walker in less than five minutes. The team then joined All JapanPro Wrestlingin the summer of 2002 and made an immediate impact defeating Keiji Mutoh and Taiyo Kea for the World Tag Team Championship on July 17, 2002. They would only make one successful title defense against Mike Barton and Jim Steele on August 30, 2002 before being stripped of the titles in October as they cancelled their appearances. They returned for the WRESTLE-1 show on January 19, 2003 losing to Keiji Muto and Goldberg.
