The Coast Range of California is young geologically and is composed of materials of low strength. Accelerated urban development in the San Francisco Bay area has created a serious landslide problem. A study of local topography and geology, plus an understanding of the forces involved, is essential to the visualization of the shape and action of a slide. This visualization should be verified by subsurface exploration before the design of corrective work. Modern equipment has simplified the construction of adequate and safe drainage works. While most slides will respond to drainage or other treatment, it is important to recognize that there are cases where it is not sound engineering to attempt correction. Mathematical analysis of landslides is approximate at best, but it does serve as an aid to judgment. Current laboratory procedures should be revised to more nearly simulate field conditions.