World Grand Prix 2000 in Yokohama, a qualifying tournament for the 2000 World Grand Prix. He was unable to do so, however, and Abidi stopped him en route to the final. Despite having lost his last two fights and failing to win a K-1 qualifying tournament, Aerts was still invited to the K-1 World Grand Prix 2000 Final at the Tokyo Dome on December 10, 2000, due to his status as one of the world's top kickboxers. At the quarter-final stage, he was given his rubber match with Cyrl Abidi. Aerts dominated the fight this time, and knocked Abidi down with a two-punch combination just seconds after the opening bell. He took a unanimous decision (29-26, 29–28, 29–26) after three rounds. However, during the fight, Abidi headbutted Aerts numerous times which caused a cut on his forehead. Due to this cut, Aerts could not advance in the tournament and was replaced by Abidi in the semis. Aerts would then KO Stuart Green in round one in a superfight at the K-1 Holland GP 2001 in Arnhem on February 4, 2001, his first fight in the Netherlands in almost six years. After a decision loss to Mirko Cro Cop at K-1 Gladiators 2001 and a TKO win over Nobu Hayashi at K-1 Burning 2001 in early 2001, he entered the K-1 World Grand Prix 2001 in Las Vegas on August 11, 2001. After knocking out Noboru Uchida in the quarter-finals of the tournament, he had his fourth fight with Maurice Smith in the semis and went 4–0 over the American with an extra round unanimous decision. In the final, he was KO'd by Stefan Leko late in the third round. At the K-1 World Grand Prix 2001 Final on December 8, 2001, Aerts went up against Francisco Filho at the first stage. Aerts developed a large hemotoma on his left foot when Filho blocked one of his kicks with his knee. Due to this, Aerts' corner stopped the fight at the end of round two and he was eliminated from the tournament. He kicked off 2002 with wins over Nicholas Pettas and Andrei Kirsanov in the first half of the year before losing a majority decision to Alexey Ignashov at the K-1 World Grand Prix 2002 in Fukuoka on July 14, 2002. He qualified for the 2002 K-1 World Grand Prix final eight when he won a unanimous decision (30-27, 30–27,