During the Vietnam War, Ayers, was a member of a radical group called the Weather Underground, responsible for a number of protest bombings, including one in a Pentagon bathroom, the Chicago Tribune reported Tuesday.
Ayers worked with Barack Obama on education reform, and the ties between the two became an issue in the 2008 presidential campaign, the newspaper said.
Ayers' retirement had nothing to do with the negative press, UI Education Dean Vicki Chou said, adding that the university will miss him.
"It will be more than a ripple because he's made a significant mark here," Chou said. "He's been really a very good colleague here. He has hundreds of students who really cherish that they've had the experience of being taught by him."