Dipole polarizabilities of Ge-n clusters with 2-25 atoms are calculated using finite field (FF) method within density functional theory. The dipole moments and polarizabilities of clusters are sensitively dependent on the cluster geometries and electronic structures. The clusters with low symmetry and large HOMO-LUMO gap prefer to large dipole moments. The polarizabilities of the Ge-n clusters increase rapidly in the size range of 2-5 atoms and then fluctuate around the bulk value. The larger HOMO-LUMO gap may lead to smaller polarizability. As compared with the compact structure and diamond structure, the prolate cluster structure corresponds to a larger polarizability. (C) 2002 Published by Elsevier Science B.V.