This book constitutes the refereed proceedings of the 5th International Conference on Extreme Programming and Agile Processes in Software Engineering, XP 2004, held in Garmisch-Partenkirchen, Germany in June 2004. The 23 revised full papers presented together 10 revised short papers, 8 demonstration papers, 4 educators' track papers, and various workshop and panel summaries were carefully reviewed and selected from 69 submissions. The papers are organized in topical sections on acceptance testing, scalability issues, new insights, refactoring, social issues, and practitioner reports.