The Nevada Seismic Zone has historically been one of the most active seismic regions of the intermountain west. Although all large (M>7.0) earthquakes located within this zone occurred prior to the establishment of a worldwide seismograph network, most have been well recorded instrumentally. This study uses available instrumental data to determine the source parameters for some of the earliest earthquakes occurring within the region, namely, the 1915 (M=7.6) Pleasant Valley and 1932 (M=7.2) Cedar Mountain earthquakes, and several smaller events of 5.5≤M≤6.5 occurring within the Cedar Mountain region between 1934 and 1943. Results of body waveform inversions suggest that the Pleasant Valley earthquake, at the northern end of the Nevada Seismic Zone, is a complex event best fit by a multiple source-time function. Waveform and first-motion information for the Cedar Mountain earthquake, located within the Walker Lane, suggest the earthquake was composed of two events, each having significant components of right-lateral strike-slip motion (rakes of -176¿ to -179¿). Waveforms of the M=6.5 Excelsior Mountain earthquake, located only 40 km southwest of Cedar Mountain, suggest the earthquake was a simple rupture along a normal fault (rake of -90¿¿20¿), although surface faulting indicates that the event had a component of left-lateral strike-slip motion. ¿ American Geophysical Union 1988