This book honors Professor Antoni Mazurkiewicz, who during his long scientific career (in 2006 he celebrated 50 years of employment in the academic world) made fundamental contributions to theoretical computer science. These contributions span a whole range of research areas, including the theory of programming, models of concurrent and distributed systems, (de)composition methods for Pietri nets, algorithms on graphs, synchronizing networks, and concurrent and asynchronous algorithms.He is best known for inventing the theory of traces, which became one of the cornerstones of the theory of concurrency. His ideas have inspired many scientists all over the world. Many concepts he introduced have shaped whole lines of research in concurrency. He had a tremendous influence on the development of theoretical computer science in Poland. Many of his former Ph.D. students became research leaders and today hold professorships at universities in Poland and abroad, pursuing research inspired by ideas of their mentor.