This book constitutes the refereed proceedings of the 5th International Workshop on Internet Charging and QoS Technologies, ICQT 2006, held in St. Malo, France, in June 2006 as an associated workshop of ACM Sigmetrics / IFIP Performance 2006.

The 8 revised full papers presented together with a keynote paper were carefully reviewed and selected from a total of 27 submissions. The papers are organized in topical sections on economy-driven modeling, auctions, peer-to-peer, and secure billing, thus addressing a highly interesting facet of networking research and business modelling.