This book constitutes the refereed proceedings of the 20th International Symposium on Distributed Computing, DISC 2006, held in Stockholm, Sweden in September 2006.The 35 revised full papers selected from 145 submissions are presented together with 1 invited paper and 13 brief announcements of ongoing works chosen from 26 submissions; all of them were carefully selected for inclusion in the book. The entire scope of current issues in distributed computing - theory, design, analysis, implementation, and application of distributed systems and networks - is addressed, ranging from foundational and theoretical topics to algorithms and systems issues and to applications in various fields.