Kasem is best known by name as a music historian and disc jockey, most notably as host of the weekly American Top 40 radio program from 1970 to 1988, and again from March 1998 until January 102004, when Ryan Seacrest succeeded him. He hosted a spin-off television show called America's Top 10 for a time in the 1980s. He was the host of the short-lived American version of 100% (game show) in 1999. For a period in the late 1970s and early 1980s, Kasem was the staff announcer for the NBC television network. More recently, he has appeared on infomercials about CD music compilations. Kasem was inducted into the Radio Hall of Fame in 1992. He is a graduate of Wayne State University.
From January 1989 to March 1998 when he was not at the helm of American Top 40, he was host of Casey's Top 40, Casey's Hot 20, and Casey's Countdown syndicated out of the Westwood One Radio Networks. These shows competed with his former show, American Top 40, which was hosted by Shadoe Stevens from 1988-1995.