As a result of a recommendation made in the report Geodesy: Trends and Prospects (Committee on Geodesy, 1978), a Panel on Crustal Movement Measurements was formed under the Committee on Geodesy and the Committee on Seismology of the U.S. National Research Council. The panel has prepared a very timely report that sets out to identify the key issues and to outline the directions that promise the most rapid progress toward quantifying crustal deformation in the next decade. There is definitely a need to quantify the process of strain accumulation and release over a wide range of length scales. A monitoring program to do this would serve as the basis for a renewed effort to understand the physical principles of earthquake generation and the mechanical behavior of the lithosphere in general. Faced with a bewildering array of new instruments of both the terrestrial and space-oriented variety, which are about to advance from the stage of development to the stage of field deployment, we undoubtedly need the guidance that this volume is intended to provide.