The possibility of relating seismicity to Cenozoic tectonics in the Western United States has led to the need for a compilation and a map of fault-plane solutions for this area. For several years the U.S. Geological Survey has determined fault-plane solutions from their seismograph arrays, principally in California and Nevada. These data were summarized by Lindh and others (1973). Fault-plane solutions for the Intermountain region, including Utah, Idaho, Nevada, Montana, and Wyoming, were compiled by Smith and Sbar (1974). Following these compilations, many new fault-plane solutions were published as the result of detailed analyses of earthquakes recorded by portable and new permanent seismograph arrays. Our intent here is to provide a tabulation (Table 5-1, in pocket) and map of the principal fault-plane solutions (Fig. 5-1, P1. 5-1, in pocket) for the Western United States through 1975 and part of 1976. For each fault-plane solution, the tabulations list the type of solution (single event, S; composite, C), date, time (GMT), location, attitudes of P - and T -axes, nodal-plane attitudes, and the reference. Because of the wide variety of types and sizes of seismograph arrays and the differences in data analyses, we have not attempted to analyze the quality of individual solutions; however, we have differentiated between single-event solutions (large symbols) and composite solutions (small symbols) on the map (Fig. 5-1). Generally, a single-event solution was determined from an earthquake of magnitude ( M ) 5.0 or larger, unless it was recorded within a dense array such as in the U.S. Geological Survey Nevada test-site