Correlations between topography, gravity, and areoid on Mars are used to constrain the crustal and lithospheric thicknesses on the planet. Assuming that the Hellas basin is in isostatic equilibrium with Airy compensation, point correlations between areoid anomalies and topography are used to obtain the mean crustal density and the crustal thickness. We find that the crustal thickness at the reference zero elevation is 90 ¿ 10 km. We also find that the mean crustal density is 2960 ¿ 50 kg m-3. We have also used several approaches to constrain the thickness of the elastic lithosphere. Using the spherical harmonic coefficients of the gravity potential and topography as a function of degrees, a relatively weak constraint on the globally averaged thickness of the elastic lithosphere is obtained. An improved constraint is obtained using wavelet transform analyses of great circle tracks of gravity and topography. The gravity-topography admittance as a function of wavelet wavelength constrains the globally averaged thickness of the elastic lithosphere to be in the range 90 ¿ 10 km. The observation that the mean thicknesses of the crust and elastic lithosphere are likely to be equal suggests that a rheologically tougher crust is the elastic lithosphere.