This report presents a new Geographic Information System composite map of the geologic surface effects caused by underground nuclear testing in the Yucca Flat Physiographic Area of the Nevada Test Site, Nye County, Nevada. The Nevada Test Site (NTS) was established in 1951 as a continental location for testing nuclear devices (Allen and others, 1997, p.3). Originally known as the ''Nevada Proving Ground'', the NTS hosted a total of 928 nuclear detonations, of which 828 were conducted underground (U.S. Department of Energy, 1994). Three principal testing areas of the NTS were used: (1) Yucca Flat, (2) Pahute Mesa, and (3) Rainier Mesa including Aqueduct Mesa. Underground detonations at Yucca Flat and Pahute Mesa were typically emplaced in vertical drill holes, while others were tunnel emplacements. Of the three testing areas, Yucca Flat was the most extensively used, hosting 658 underground tests (747 detonations) located at 719 individual sites (Allen and others, 1997, p.3-4). Figure 1 shows the location of Yucca Flat and other testing areas of the NTS. Figure 2 shows the locations of underground nuclear detonation sites at Yucca Flat. Table 1 lists the number of underground nuclear detonations conducted, the number of borehole sites utilized, and the number of detonations mapped for surface effects at Yucca Flat by NTS Operational Area.