Abstract This volume contains the proceedings of EWSN 2006, the third in a series of European workshops on Wireless Sensor Networks. The workshop took place at ETH Zurich from February 13 to 15, 2006. Its objective was to present, discuss, and explore the latest technical developments in the field of wireless sensor networks, as well as potential future directions. Wireless Sensor Networks has become an active and popular research area, which is witnessed by the 133 submissions we received from authors all over the world. The program committee chose 21 papers for inclusion in the workshop. It was a difficult choice, based on several hundred reviews produced by the program committee and many outside referees, where each paper was typically reviewed by three reviewers.