This book constitutes the refereed proceedings of the 10th International Conference on Passive and Active Measurement, PAM 2009, held in Seoul, Korea, in April 2009. The 22 revised full papers and 2 revised demo papers presented were carefully reviewed and selected from 77 submissions. The papers focus on research and practical applications of routing and forwarding, topology and delay, methods for large-scale measurements, wireless, management tools, audio and video traffic, peer-to-peer, traffic measurements, and measurements of anomalous and unwanted traffic.