The originality and impact of Sexual Perversity in Chicago by David Mamet and its influence on the Chicago theater scene is the focus of this chap-ter, showing how the language and subject matter of the play almost single-handily overturned Chicago theater in the 1970s. Previously a try-out town for productions headed to Broadway, or a stop for touring plays, Mamet and a cohort of young directors and actors initiated a series of experimental theaters off-Loop (out of downtown), providing a breeding ground for new plays that inverted traditional formats. Emerging out of a tradition of minor but experimental theater groups like the early Little Theatre, this new form of theater soon took shape with the Compass Players, the Organic Theater, Second City, Body Politic, and Steppenwolf. Theater took on new methods of presentation and subject matter with Mamet leading the way. With its frank talk about sex and relationships, Sexual Perversity in Chicago set the tone for new dramatic experiences, offending some but, more importantly, finding newer and younger audiences eager for unique theatrical experiences representing contemporary urban life.