The results of a Class II Cultural Resource Inventory are reported for the McCain Valley Study Area. The Study is designed to accommodate the Bureau of Land Management's (BLM) planning and management needs by providing a data base from which objective estimates can be made of the nature and distribution of cultural resources within a defined area. Located in eastern San Diego County, the McCain Valley Study Area is a physiographically transitional region comprised of approximately 98,000 acres of mountain and desert lands administered by BLM. Qualitative and quantitative analysis of the prehistoric sites and features and their environmental associates was used to predict the kind, density, diversity, and potential for sites throughout the entire McCain Valley Study Area. Special studies were performed for rock art and roasting pits, and on limited field collections of obsidian, ceramics, and projectile points.