During the 1986 AGU Fall Meeting in December, four Global Positioning System (GPS) receivers were demonstrated in a simulated field condition. Although billed as a “shootout,” constraints of time and location dictated that this demonstration would not be a valid test of the receivers, and in retrospect, it should not be viewed as such. Nevertheless, there may be some interest in the results. The experiment involved the Macrometer II™, manufactured by Litton Aero Service; the WM 101, manufactured by a joint venture of Wild-Heerbrugg and Magnavox; the Trimble 4000 S; and the Texas Instruments TI 4100. The first three were operated by representatives of the manufacturers. The TI4100 instruments were owned and operated by the U.S. Geological Survey.