An analysis of the gravity field in two largely Precambrian metamorphic rock areas of Australia, one in the southwestern and the other in the central part, indicates that the regional Bouguer anomalies may be explained by models of the crust and upper mantle consistent with the other geophysical and geological observations. In the southwestern part, the longer wavelength component of the anomalies is consistent with a crust which has been determined by seismic measurements to be greater than normal in thickness and density in the west owing to the presence of a high-velocity basal layer that thins out eastwards. The shorter wave-length components show excellent correlation with the near-surface geology. In central Australia, where no comparable seismic measurements have been made, the Bouguer anomaly field, which is dominated by large amplitude (up to 150 mGal) and long wavelength (about 150 to 200 km) components, is interpreted in terms of thickness and structure of a two-layer crust. The derived crustal model is based on the concept of folding and faulting that involves the entire crust and upper mantIe, and is compatible with the broad aspects of surface geology and structure. The crustal upwarps in the model, with the intermediate and Mohorovicic discontinuities at depths as shallow as 15 and 27 km, are associated with the Arunta and Musgrave Blocks, where deep crustal rocks are exposed against large thrust faults. The crustal downwarps, with the discontinuities as deep as 31 and 43 km, are associated with basins containing substantial thicknesses of sediments. Depths to these discontinuities are in agreement with those estimated from the only two isolated deep seismic reflection probes in the basin areas.