Kent Beck developed his process model Extreme Programming (XP) (Beck 2000) in the context of the Chrysler project Chrysler Comprehensive Compensation (C3), which aimed to develop payroll software (Beck and Andres 2004). At the time Beck joined, the project was already on the verge of failure. Beck was therefore given the opportunity to formulate his initially informal agile project practices as a new process model. To this end, Beck developed values, principles, and XP practices, which are presented and evaluated in detail here.