This book contains the final reports of 19 workshops held during the 20th European Conference on Object-Oriented Programming, ECOOP 2006, held in Nantes, France in July 2006.The 19 reports cover the entire range of object technology and related topics. Their contents was provided by the respective workshops organizers and picked out in a twofold selection process. Thus the reports present a coherent and highly representative snapshot of the major trends in the field.