  The effect of deformation on the excitation of multiple giant dipole
resonances is studied. Analytical expressions are derived in the framework of
the interacting boson model for the energies and E1 properties of giant dipole
resonances in spherical and deformed nuclei, and a numerical treatment of
transitional nuclei is proposed. Coulomb-excitation cross sections are
calculated in $^{238}$U and in the samarium isotopes.
