The High Resolution Fly’s Eye Detector (HiRes) detects and measures properties of ultra high energy,E>1018&hthinsp;eV,cosmic rays. HiRes exploits what is known as the “Air Fluorescence” technique which uses the atmosphere as a calorimeter. A brief description of this technique and how it is used by the HiRes detector will be given in this paper. The HiRes detector has been operational with two detector sites separated by 12.6 km since spring 1999. The two separated “eyes” enable the HiRes detector to obtain stereoscopic observations of the air showers. We also have a data set obtained with the first of the 2 sites from 2.5 years of observations in monocular mode. Preliminary results from both the monocular and stereo analysis will be described. ©2001 American Institute of Physics.