This book constitutes the thoroughly refereed post-proceedings of the 7th International Symposium on Privacy Enhancing Technologies, PET 2007, held in conjunction with WOTE 2007, the IAVoSS Workshop on Trustworthy Elections. The papers 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.