 While he was a student at Florida, he became a member of the Phi Delta Theta fraternity.Prior to serving as Rice University president, Gillis was Dean of the Faculty of Arts and Sciences at Duke University (1991–1993) and Dean of the Graduate School and Vice Provost for Academic Affairs at Duke (1986–1991).Gillis helped to found Jacobs University Bremen (initially International University Bremen) and served on the board of governors.