This book constitutes the reviewed proceedings of the Fourth International Workshop on Algorithmic Aspects of Wireless Sensor Networks, ALGOSENSORS 2008, held in Reykjavik, Iceland, Wroclaw, Poland, July 12, 2008. The workshops aimed at bringing together research contributions related to diverse algorithmic and complexity-theoretic aspects of wireless sensor networks. The topics include but are not limited to optimization problems, noise and probability, robots and tours.