Seasonal and annual changes were determined in species composition and population densities of phytophagous and predaceous mites on three species of native pines (Pinus coulteri, P. lambertiana, and P. ponderosa) in the San Bernardino Mountains. Population trends were recorded for the Phytoseiidae, Tetranychidae, and Tenuipalpidae. Four species of tetranychids of the genus Oligonychus were present, one species of phytoseiid, Metaseiulus validus, and the tenuipalpid, Brevipalpus sp. Mite numbers were generally lowest from January to March. Predaceous mites gave a positive numerical response to increases in tetranychid population.