Foster, 62, plans to remain as a faculty member teaching music education classes.
He said he thought it was time for someone else to lead the program.
"I've been teaching band and other things for 41 years. That's a long time," he said. "I think a change will do everybody good."
The School of Fine Arts plans to form a search committee soon to find Foster's replacement.
In his time at KU, Foster has participated in 30 commencements, 31 opening convocations, hundreds of concerts and more than 150 football halftime shows.
"My belief has always been that outside of athletics there's nothing more visible than the band, and it is important for the band to be good and to be respected for its quality and class," Foster said.
The band program Foster now leads is much larger than the one he started with in 1971. Now the program has 11 bands with more than 600 members. His additions include the University Band, Symphonic Wind Ensemble, an academic jazz program and 128 more members in the marching band.
But some things about the program haven't changed.
"People like to be entertained," he said.
Foster is only the fifth man to lead KU bands in the 100-plus years they've been around.
In 1983, he was selected by The School Musician magazine as one of the top 10 music educators in the nation. In 1988, he was named Outstanding Band Director by the Kansas Bandmasters Assn. and Phi Beta Mu. Last year, he was presented the Distinguished Service to Music Medal by Kappa Kappa Psi, a national award.
Before coming to KU, he taught at the University of Florida and at public schools in Austin and Houston, Texas.
-- Staff writer Terry Rombeck can be reached at 832-7145.