Wireless sensor network (WSN) is a promising new technology. It could be a way to achieve ubiquitous computing and embedded Internet. WSNs are an efficient solution for applications that involve deep monitoring of a deployment environment. The objective of this thesis is to explore the use of WSNs for object tracking and motion estimation. It introduces the WSN technology, their theoretical characteristics, system constraints, WSN architectures, deployment topologies and standards. The object-tracking system that this thesis introduces, demonstrates a real-world application that uses a WSN to track objects and communicate their information. It is an event-driven application implemented in Java, built on top of the Crossbow MSP 410 wireless sensor system. The algorithm process the data returned from the WSN detection signals and tracks the object's motion. Deployment scenarios are proposed that demonstrate suitable node topologies for the system. The evaluation of the object-tracking system is performed by conducting a number of indoor and outdoor experiments. Thesis Advisor(s): Gurminder Singh, Arijit Das. Thesis (M.S. in Computer Science)--Naval Postgraduate School, September 2005. Includes bibliographical references (p. 271-273). System requirements: Adobe Acrobat reader.