This book constitutes the refereed proceedings of the 12th International Conference on Parallel Computing, Euro-Par 2006. The book presents 110 carefully reviewed, revised papers. Topics include support tools and environments; performance prediction and evaluation; scheduling and load balancing; compilers for high performance; parallel and distributed databases, data mining and knowledge discovery; grid and cluster computing: models, middleware and architectures; parallel computer architecure and instruction-level parallelism; distributed systems and algorithms, and more.