Precise geodetic surveys were made before and after the JORUM underground nuclear explosion, which was detonated September 16, 1969, at the U. S. Atomic Energy Commission's Nevada Test Site. Strains calculated from these surveys show a relationship of the strain directions and magnitudes to the volcanic caldera collapse system of this area. Strains within the area 20 collapse zone show northwesterly compression and are similar in magnitude, whereas strains in other collapse zones are generally smaller and of different orientations. Distance was monitored over a 2-km range from hr after the explosion to 5 days later. Five steplike distance changes were recorded during the first hr of monitoring and none was recorded after that. One of the steps was in conjunction with an identifiable seismic event.