Wireless ad-hoc sensor networks have recently become a very active research subject due to their high potential of providing diverse services to numerous - portant applications, including remote monitoring and tracking in environm- tal applications and low-maintenance ambient intelligence in everyday life. The e?ective and e?cient realization of such large-scale, complex ad-hoc networking environmentsrequiresintensive,coordinatedtechnicalresearchanddevelopment e?orts,especiallyinpower-aware,scalable,robust,wirelessdistributedprotocols, due to the unusual application requirements and the severe resource constraints of the sensor devices. On the other hand, a solid foundational background seems necessary for sensor networks to achieve their full potential. It is a challenge for abstract modeling, algorithmic design and analysis to achieve provably e?cient, sc- able and fault-tolerant realizations of such huge, highly dynamic, complex, n- conventionalnetworks.Variousfeatures,includingtheextremelylargenumberof sensor devices in the network, the severe power, computing and memory limi- tions,theirdense,randomdeploymentandfrequentfailures,posenewinteresting abstract modeling, algorithmic design, analysis and implementation challenges of great practical impact. This workshop aimed to bring together research contributions related to diversealgorithmicandcomplexitytheoreticaspects ofwirelesssensornetworks. This was the third event in the series. ALGOSENSORS 2004 washeld in Turku, Finland, ALGOSENSORS 2006 was held in Venice, Italy. Since its beginning, ALGOSENSORS has been collocated with ICALP. The Third International Workshop on Algorithmic Aspects of Wireless S- sor Networks (ALGOSENSORS 2007) was organized by Wrocla w University of Technology.TheworkshopwasheldonJuly14,2007,inconjunctionwithICALP 2007. After a careful review by the Program Committee of 25 submissions, 11 regular papers were accepted to ALGOSENSORS 2007. Apart from the regular talks, two keynote speeches were given at the workshop.