This book constitutes the refereed proceedings of the 4th Conference on Extreme Programming and Agile Methods, XP/Agile Universe 2004, held in Calgary, Canada in August 2004. The 18 revised full papers presented together with summaries of workshops, panels, and tutorials were carefully reviewed and selected from 45 submissions. The papers are organized in topical sections on testing and integration, managing requirements and usability, pair programming, foundations of agility, process adaptation, and educational issues.