This paper describes the components and an addressing scheme for a sensor network in which the number and location of sensor nodes change dynamically. A sensor network is a network composed of various sensor nodes, and a sensor node consists of one or more CPUs, sensors, and a network interface. A sensor network, an organization of sensor nodes that are embedded in a wall, floor, electrical equipment, and nonelectrical equipment, can be used to support human action, the navigation of mobile robots, and other purposes. In comparison with a closed sensor network in a factory, they have the possibility to be moved somewhere without any notice given to the network management system. In order to operate such networks effectively and correctly, changes of the number and location of sensor nodes must be detected. In this paper, we discuss some fundamental components of such a network, and we call a network having these components an adaptive sensor network. They include position‐based addressing, an addressing scheme that can be generally applicable to the construction of such sensor network systems. With this addressing scheme, a data value is requested by using not an identifier but a location. The client that requests the data does not care whether there is a real sensor node at the location or not. We created a prototype of an adaptive sensor network system. It consists of a node management system, a node positioning system, and a human interface system for the sensor network. Through performance evaluation of the prototype, we concluded that it could follow dynamic changes due to either node failures or the motion of nodes. © 2000 Scripta Technica, Electron Comm Jpn Pt 3, 84(3): 62–71, 2001