Measurements of SKS phase splitting were obtained from nineteen seismic stations in southern California. The fast polarization directions are 53¿ at the southern end of the Great Valley, 82¿8¿ in the western Transverse Ranges and northern Peninsular Ranges, 95¿4¿ in Mojave Desert, and 70¿ on San Clemente Island. The splitting time ranges from 0.8 to 1.8 seconds, which is consistent with an anisotropic layer of 100 to 200 km thick for 4% anisotropy. ¿ American Geophysical Union 1995