Eight protonated germane structures (GeH5+) were examined in detail using the self-consistent field (SCF), configuration interaction including single and double excitations (CISD), and coupled cluster including single, double, and perturbatively included triple excitations [CCSD(T)] methods in conjunction with a double-zeta plus polarization (DZP) and a triple-zeta plus polarization (including f functions on germanium TZP+f) basis set. The C-4 upsilon and the D-3h isomers are high in energy [84 and 48 kcal mol(-1), respectively, relative to the C-s(I) structure at DZP SCF]. Although structure C-s(I) is the global minimum, both C-s structures, where GeH5+ is comprised of a nearly planar germyl cation and a hydrogen molecule, are essentially equal in energy and allow virtually free hydrogen moiety rotation. Complete hydrogen scrambling does not occur, as the energy of the C-2 upsilon(I) structure [33 kcal mol(-1) (TZP+f CCSD)] is higher than the dissociation energy of GeH5+ into GeH3+ and H-2 (D-0=10 kcal mol(-1)). D-0 of GeH5+ is almost the same as for SiH5+ due to a favorable highest 5 occupied molecular orbital (HOMO) (sigma(H2))-lowest unoccupied molecular orbital (LUMO) (P-Ge) interaction in GeH5+. The global minimum was characterized by vibrational frequency analyses, (up to TZP+f CCSD), and we also report on the rotational constants as well as the proton affinity of germane (156 kcal mol(-1)).