This paper summarizes the ongoing work at the University of Texas to develop a class of passive, wireless sensors to detect corrosion in reinforced concrete structures. Two prototype sensors have been developed that are designed to be attached to the reinforcing cage before the concrete is placed. The basic and improved sensors are inexpensive to fabricate, sufficiently durable to survive the construction process, can be interrogated through concrete, and provide reliable information about the initiation of corrosion in the adjacent reinforcement. Because the sensors do not contain an internal battery, the expected life of the sensors is expected to be essentially the same as the design life of the structure in which they are embedded.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.