The Pendleton (Oregon) Project, conducted between September 1968 and May 1970, was designed to study in detail the effects of meteorological conditions on sonic booms. Data consisted of booms of opportunity resulting from U.S. Air Force SR-71 training missions, flying at or above 20 km faster than Mach 2.5. These were recorded by a dense grid and line array of self-activated microphone-recorder systems; results were compared with those computed by the ARAP sonic boom propagation program using the observed as well as the standard atmosphere. A total of 46 sonic booms, involving over 1800 signatures, were selected for the final analysis. Meteorological data consisted of conventional upper-air soundings to above aircraft level, and routine, detailed sampling of boundary layer structure and turbulence by means of a specially instrumented light aircraft.