It was 1999 when Extreme Programming Explained was ?rst published, making this year s event arguably the ?fth anniversary of the birth of the XP/Agile movement in software development. Our fourth conference re?ected the evolution and the learning that have occurred in these exciting ?ve years as agile practices have become part of the mainstream in software development. These pages are the proceedingsof XP Agile Universe 2004, held in beautiful Calgary, gateway to the Canadian Rockies, in Alberta, Canada. Evidentintheconferenceis thefactthatourlearningis still inits earlystages. While at...