Gravity gradiometry was one of the first geophysical measurements used in petroleum exploration early in this century, but with the development of accurate relative gravity meters, gradiometer measurements have not been used for geologic studies until recently. Conceptually, the fundamental measurement is the difference between a matched pair of accelerometers. Since they are linked together physically, common mode accelerations are eliminated, resulting in a measurement that is not sensitive to local platform motion. In a moving-platform environment, short-wavelength noises are attenuated significantly in the gradiometer output. Once converted back to conventional gravity by integration, the gradient signal can be combined optimally with the conventional gravity signal to extend the bandwidth to the shorter wavelengths. This means that a gradiometer system is suited ideally for acquiring data in rough seas or from aircraft. The gradients it measures provide valuable cross-line information about the causative body, much in the way a swath of seismic data provides cross-line information that a single 2-D seismic line lacks. This greatly enhances the information content of a gradiometer survey over a conventional gravity survey, especially in reconnaissance surveys with widely spaced traverses.