This book constitutes the refereed proceedings of the 9th International Symposium on Privacy
Enhancing Technologies PETS 2009 held in Seattle WA USA in August 2009. The 14 revised
full papers presented were carefully reviewed and selected from 44 initial submissions. The
papers - both from academia and industry - cover design and realization of privacy services for
the internet and other communication networks and present novel research on all theoretical and
practical aspects of privacy technologies as well as experimental studies of fielded systems.
