The motion of a linear array of monuments extending across the Eastern California Shear Zone (ECSZ) has been measured from 1994 to 1999 with the Global Positioning System. The linear array is oriented N54 ¿E, perpendicular to the tangent to the local small circle drawn about the Pacific-North America pole of rotation, and the observed motion across the ECSZ is approximated by differential rotation about that pole. The observations suggest uniform deformation within the ECSZ (strike N23 ¿W) (26 nstrain yr-1 extension normal to the zone and 39 nstrain yr-1 simple right-lateral shear across it) with no significant deformation in the two blocks (the Sierra Nevada mountains and southern Nevada) on either side. The deformation may be imposed by right-lateral slip at depth on the individual major fault systems within the zone if the slip rates are: Death Valley-Furnace Creek fault 3.2¿0.9 mm yr-1, Hunter Mountain-Panamint Valley fault 3.3¿1.6 mm yr-1, and Owens Valley fault 6.9¿1.6 mm yr-1. However, this estimate of the slip rate on the Owens Valley fault is 3 times greater than the geologic estimate.