Sensor and data fusion is a process of paramount importance for many domains and applications. Its potential for rapid data and information processing are of primary importance for surveillance, security, intelligent transportation systems, navigation and communications. Effective use of the data requires the sensor and context data to be aggregated or “fused” in such a way that high quality information results and serves as a basis for decision support. Data fusion encompasses groups of methods for merging various types of data and information. This process is especially important for tracking systems. This chapter presents taxonomy of sensor data fusion methods. Applications from object tracking in video are presented.