The abundance and diversity of arthropods present in the surface soil layers at various forest sites in northern California were investigated, primarily at two old-growth redwood forest sites in Prairie Creek Redwoods State Park and Jedediah Smith Redwoods State Park. A wide variety of arthropods were found, including representatives of Araneae, Pseudoscorpiones, Opiliones, Acarina, Isopoda, Diplopoda, Chilopoda, Symphyla, Pauropoda, Protura, Diplura, Collembola, Thysanoptera, Hemiptera, Coleoptera, Diptera, and Hymenoptera. Arthropod densities were significantly higher in the wet than in the dry period, indicating seasonal variation in surface densities of soil arthropods. The densities of arthropods in soils collected from beneath coast redwood (Sequoia sempervirens) and western hemlock (Tsuga heterophylla) trees were not significantly different.