We demonstrate that the excess dynamic ellipticity of the core-mantle-boundary (CMB) inferred from the period of the Earth's retrograde free core nutation (RFCN) may be explained in terms of viscous stresses generated by mantle convective flow. The 3D elastic structure and radial viscosity profile which define the model used in the viscous flow calculations are constrained to simultaneously reconcile a large set of seismic and geodynamic data. ¿ American Geophysical Union 1995