In regions of slowly varying lateral density changes, the gravity and geoid anomalies may be expressed as power series expansions in topography. To a good approximation, geoid anomalies in isostatically compensated regions can be directly related to the local dipole movement of the density-depth distribution. This relationship is used to obtain theoretical geoid anomalies for different models of isostatic compensation. The clasical Pratt and Airy models give geoid height-elevation relationships differ in their functional form but which predict geoid anomalies of comparable magnitude. The thermal cooling model which explains ocean floor subsidence away from mid-ocean ridges predicts a linear age-goid height relationship of 0.16 m/m.y. Geos 3 altimetry profiles were examined to test these theoretical relationships. A profile over the mid-Atlantic ridge is closely matched by the geoid curve derived from the thermal cooling model. The observed geoid anomaly over the Atlantic margin of North America can be explained by Airy compensation. The relation between geoid anomaly and bathymetry across the Bermuda Swell is consistent with Pratt compensation a 100-km depth of compensation.