The Pn arrivals recorded from the southern California array have been used to demonstrate regional variation in crustal thickness and Pn velocity and to investigate the presence of anisotropy in the mantle. Over 2800 travel times we used in the analysis. The classical time term method was extended to allow the Moho velocity to vary in a block-type structure. The statistical F test shows these effects to be significant. Crustal delays determined depend on both crustal velocities and Moho depth. The Ventura and Los Angeles basins have sediment delays which indicate sediment thicknesses near 10 km. The Moho depth itself varies by 10 km over southern California with a mean of about 29 km. Slightly thicker crust is prevalent in the northwestern corner of the array near the Southern Coast Ranges. Five kilometers of rapid thinning between the coast and the Channel Islands is shown by a sharp gradient in the delay times. Normal crustal thicknesses occur over the rest of the array except for the area east of the Salton Trough, where an anomalously thin crust of 22 km exists. This area extends from near the plate bondary into Arizona. While the Peninsular Ranges and the San Bernadino Mountains have small roots, the San Gabriel Mountains have none. Pn velocities range from 7.6 to 8.2 km/s within the array. High velocities are found in the Mojave and offshore regions. Low velocities are found in the Peninsular Ranges and the Transverse Ranges. The analysis supports a mean anisotropy of 0.15 km/s with the fast direction at N 75¿ W. This value represents an average of a parameter that varies considerably in the region.