This book constitutes the refereed proceedings of the 13th International Conference on Passive and Active Measurement, PAM 2012, held in Vienna, Austria, in March 2012. The 25 revised full papers presented were carefully reviewed and selected from 83 submissions. The papers were arranged into eight sessions traffic evolution and analysis, large scale monitoring, evaluation methodology, malicious behavior, new measurement initiatives, reassessing tools and methods, perspectives on internet structure and services, and application protocols.