The Earth is the yardstick against which the state of isostasy on the terrestrial planets will be assessed in the future. The primary data sets will continue to be gravity anomaly and topography data together with seismic data which have the potential to image the surfaces of flexure directly. We are close to defining the relative contributions of plate flexure and mantle dynamics in contributing to Earth’s topography and gravity fields as well as to its crustal structure and vertical motion history. The acquisition of higher-resolution data will increase the number of estimates of Te of the planets which, in turn, will help us to understand better the complexities of their geodynamical evolution.