We have used the coherence between Bouguer gravity and topography to determine the elastic thickness (Te) of the lithosphere in central Canada. In order to improve the resolution, we have estimated the spectra with the maximum entropy method. The variations in elastic thickness delineate three main regions: (1) The Interior Platform where Te varies between 25 and 50 km; (2) The Shield includes several high rigidity cores, in particular in the Trans-Hudson orogen and in the Hearne Province where Te>80 km; (3) The Hudson Bay basin has an elastic thickness between 50 and 70 km with higher values in the eastern part. The results suggest that Te is controlled by the thermal regime in the platform. There is no difference in Te between the Proterozoic and Archean Provinces of the Shield. In the platform, the elastic thickness is lowest where sediments are thickest, indicating that low rigidity has amplified the subsidence of the basin. ¿ 1999 American Geophysical Union