This issue of the Bulletin of the Seismological Laboratory summarizes the determination of epicenters for earthquakes located in the western Great Basin, Nevada and eastern California, for the period 1975-1979. The Laboratory attempts to identify and locate all earthquakes with ML greater than about 2.5 in this region. Quality of locations is best for events located in areas with dense seismic coverage; events well outside the network (aftershocks of NTS explosions, etc.) may be mislocated by several tens of kilometers.