Williams was a top player in Illinois upon his graduation from Rolling Meadows High in 1989 and was recruited by Xavier University. He was undrafted after a college career at Xavier University, and has played for the Utah Jazz, Milwaukee Bucks, Denver Nuggets, Vancouver Grizzlies (now Memphis Grizzlies), Seattle SuperSonics, Washington Wizards, New Jersey Nets, Toronto Raptors, and New Orleans/Oklahoma City Hornets.
In 2000-01, Williams posted his best numbers as a pro, playing all possible 82 games while averaging 10.1 points and 7.2 rebounds per game, but also had the dubious distinction of leading the league in total personal fouls committed, with 319 (an average of 3.89 fouls per game).
On December 17, 2004, he was traded by the New Jersey Nets to the Toronto Raptors along with Alonzo Mourning, Eric Williams, and two first round draft picks in exchange for Vince Carter. On January 31, 2006, he was traded by the Raptors to the Hornets in exchange for two second-round draft picks.
His most common nickname is "A-Train".