On November 23, 1992, De la Hoya made his pro debut. He went on to win titles in 6 different weight divisions and beat former and current world champions Troy Dorsey (KO 1), Jimmy Bredahl, (KO 10), Jorge Paez, (KO 2), Genaro Hernandez (TKO 6), John John Molina (W 12), Rafael Ruelas (TKO 2), Julio Cesar Chavez (TKO 4, KO 8), Miguel Angel Gonzalez (W 12), Jesse James Leija (KO 2), Pernell Whitaker (W 12), Hector "Macho" Camacho (W 12), Ike Quartey (W 12), Arturo Gatti (KO 5), Francisco Javier Castillejo (W 12), and Fernando Vargas (KO 11). His only losses include a controversial majority decision loss to Félix Trinidad and two close decision losses to Shane Mosley. Oscar has been stopped only once in his entire career by the much larger Bernard Hopkins (KO 8).
On September 14, 2002, Oscar fought his nemesis "Ferocious" Fernando Vargas. After fiercely competitive early rounds, Oscar seized control of the latter half of the fight. In round 11, Oscar De la Hoya dropped Fernando Vargas with a left hook. Fernando Vargas got up at the count of nine, but De la Hoya finished him with a barrage of punches forcing the referee to stop the fight at 1:48 of round 11(TKO 11). It was later revealed that Fernando Vargas had tested positive for steroids in his post-fight drug test.
On May 3, 2003, as part of the Cinco de Mayo festivities, he retained his WBC and WBA world junior middleweight championships, when the corner of his rival, former world champion Yori Boy Campas threw in the towel, indicating that they were giving up, and officially gave De la Hoya a seventh round knockout win. On September 13, he and former rival Mosley met once again, in Las Vegas, and Mosley once again took away De la Hoya's world title belts, with a 12 round unanimous decision over The Golden Boy. This decision was met with a great deal of controversy, as De la Hoya was seen by many as the better fighter that night.
On February 9, 2004, the FBI announced it would investigate whether the rematch with Mosley had been fixed, placing Arum's promoting company, Top Rank, in the middle of a scandal that allegedly involved bribing the judges so they would score the fight for Mosley. No evidence of fixing was discovered.
De la Hoya next challenged Felix Sturm for the WBO world middleweight title on June 5, 2004. He won that fight by a disputed unanimous decision to become the first boxer in history to win world titles in 6 different weight divisions. After that, he hoped to unify that title with the three other world middleweight championships, held by Bernard Hopkins, on September 18.
He lost to Hopkins by a ninth round knockout. A left hand to the body sent him to the canvas, knocking De la Hoya out for the first time in his career. Hopkins would later join De la Hoya's Golden Boy Promotions, a boxing promotion firm.
--Wikipedia
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