The presentation and paper will include a basic description of the Giant Magnetoresistive Ratio (GMR) effect, and will describe the magnetic, electronic and thermal performance of GMR materials. A functional automotive grade magnetic rotational wheel speed sensor using GMR materials as a sensing element has been fabricated. Performance data and some design considerations will be discussed.GMR materials have been integrated with standard silicon semiconductor processing allowing sensor and signal processing circuitry to be combined on a single chip. This single chip solution allows for a high performance small sized device. The ABS sensor is a zero speed, two wire device with an output current that switches between two levels, producing a square wave that has a frequency equal to the frequency of the target wheel teeth or magnetic poles. The device has a 50% +/- 10 duty cycle over the operating temperature and frequency ranges. Air gap performance of 3mm has been demonstrated with a module 2.5 target wheel.