This book constitutes the refereed proceedings of the 19th European MPI Users' Group Meeting, EuroMPI 2012, Vienna, Austria, September 23-26, 2012. The 29 revised papers presented together with 4 invited talks and 7 poster papers were carefully reviewed and selected from 47 submissions. The papers are organized in topical sections on MPI implementation techniques and issues, benchmarking and performance analysis, programming models and new architectures, run-time support, fault-tolerance, message-passing algorithms, message-passing applications, IMUDI, improving MPI user and developer interaction.