The lowest-energy structures of Ge-2-Ge-33 have been optimized using all-electron DFT method. The properties of the germanium clusters including binding energies, second order differences in energy, HOMO-LOMO gaps, and especially fragmentation energies and fragmentation behavior have been studied. Our calculation shows that the fragmentation products of Ge-6, Ge-7, and Ge-10 clusters are abundant and appear frequently in fragmentation processes, which is consistent with the experimental observations. (C) 2008 Elsevier B.V. All rights reserved.