This book constitutes the refereed proceedings of the 8th International Conference on Agile Processes in Software Engineering and eXtreme Programming, XP 2008, held in Limerick, Ireland, in June 2008.Out of 54 submitted papers, 16 were accepted as full papers, 4 experience reports, 14 poster papers, 9 workshop papers, and 3 contributions on panel discussions. The papers are organized in topical sections on agile innovations, adaptation of agile, agile testing and assessment, history and evolution of agile, people factors in agile environments, conceptual models of agility, and experience reports.