Teleseismic P-wave travel-times measured in the eastern Great Basin show ~1 sec variations in travel-time residuals. Inversion of these data images an alternating sequence of high- and low-velocity upper-mantle bodies trending NE across the eastern margin of the Great Basin. Low-velocity mantle lies beneath the volcanic trends of the eastern Snake River Plain and the St. George volcanic field. These two low-velocity trends are separated by high-velocity mantle extending from northern Utah to SW Wyoming. Combining these results with seismic data from the western Great Basin reveals a continuation of these upper-mantle trends across the Great Basin. ¿ American Geophysical Union 1990