A method for calculating deformation, gravity and potential changes induced by volcanic loads imposed within and on the earth's crust is presented. The method involves application of techniques developed for earthquake loading problems in elastic-gravitational earth models. By considering the elastic-gravitational equilibrium of the layered system, the gravitational and displacement response due to intruding masses and to pressurized magma chambers can be computed. For applications involving seamount loading, variations in the height of sea level can be calculated by requiring that seawater lie along an equipotential. In continental loading problems the change in potential can be used to calculate the orthometric height cahnge as distinct from the geometric height change. For some plausible loading geometries, the difference between these two qunatities can be significant. Results for various loads and earth structures are shown and discussed. In particular, a magmatic mass intruding into an elastic-gravitational lithosphere overlying a compressible, gravitating asthenosphere produces distinct gravity anomalies which depend on the depth of intrusion. Applications of this result can be made to problems of isostatic compensation. The intrusion of a magmatic mass, together with the associated pressurization of the magma chamber, produces distinctive surface gravity and deformation in the near field. Gravity gradients, defined as surface gravity divided by uplift, vary with distance from the source. Moreover, orthometric elevations can be significantly (25%) less than geometric elevations. These results have clear application to data from events such as the posteruption deflation of Kilauea volcano.